Columbia  ^Hnibersitp 
in  tjje  Cttj>  of  Jgeiu  gorfe 

COLLEGE  OF  PHYSICIANS 
AND   SURGEONS 


Reference  Library 

Given  by 


'^ttzi^ 


QUESTIONS  AND  ANSWERS 


IN 


PHYSIOLOGICAL 
CHEMISTRY 

WITH 

COMMON  TESTS,  FORMUL.^,  EQUATIONS 
AND  PAST  EXAMINATION  PAPERS 

FOUNDED  ON  THE  COURSE  IN  PHYSIOLOGICAL 

CHEMISTRY,   GIVEN   AT 

THE  COLLEGE  OF  PHYSICIANS  AND  SURGEONS, 

COLUMBIA    UNIVERSITY, 

NEW  YORK  CITY 

BY 

EDWARD    C.   BRENNER,  A.B. 


NEW  YORK 

PUBLISHED    BY    THE    AUTHOR 

1906 


Copyright,  1906 
By  Edward  C.  Brenner 


Press  of 
Th'.  New  Era  pptNTiNe  Compamv. 

LANCASTER,  Pll. 


TO 
DR.  WILLIAM   J.  GIES 

IN  TOKEN  OF  THE  MANY  ACTS  OF 
KINDNESS  SHOWN  THE  AUTHOR 


PREFACE. 

This  little  book  has  been  written  to  aid  medical  stu- 
dents in  obtaining  a  clear  and  concise  idea  of  the  essen- 
tials of  physiological  chemistry.  Special  care  has  been 
taken  to  select  for  treatment  such  questions  as  best  serve 
to  make  clear  the  fundamental  principles. 

A  few  sentences  have  been  copied  verbatim  from  stan- 
dard authors.  My  reference  works  were:  the  notes  and 
lectures  of  Prof.  Gies  and  Prof.  Chittenden,  Hammar- 
sten's  "  Physiological  Chemistry,"  Foster's  and  Kirke's 
''  Physiology  "  and  Curtman's  '*  Urine  Analysis." 

I  owe  my  sincerest  thanks  to  Dr.  Gies,  without  whose 
kind  encouragement  this  would  not  have  been  attempted. 
I  am  also  under  obligations  to  Mr.  George  H.  Humph- 
reys for  assistance  in  proof  reading,  and  Dr.  Harold  M. 
Hays  for  many  valuable  suggestions. 

E.  C.  B. 

January,  1906. 


Questions  and  Answers  in 
Physiological  Chemistry. 


What  is  physiological  chemistry  ? 

Physiological  chemistry  is  chemistry  applied  to  life  phe- 
nomena, or  that  department  of  physiology  which  depends 
upon  chemistry.  It  is  chemistry  applied  to  organisms 
to  understand  their  chemical  changes  of  a  functional 
character. 

What  are  the  general  characters  of  chemical  change 
(a)  in  the  living  body,  (b)  in  the  dead  organism, 
(c)  in  plants  as  contrasted  with  animals? 

(a)  The  living  body  is  constantly  taking  in  material 
and  changing  it,  in  a  regular  and  orderly  fashion.  This 
metabolic  process  is  one  of  analysis  and  synthesis,  chiefly 
analysis,  (b)  In  the  dead  organism,  instead  of  this  proc- 
ess proceeding  in  an  orderly  fashion,  the  changes  occur 
promiscuously,  and  all  result  in  converting  the  body  into 
simpler  materials.  Thus  in  animals  there_js_an^  orderly 
analytic  and  synthetic  process ;  in  the  dead  organism,  a 
disorderTy  analytic.  (c)  Plants  convert  inorganic  into 
organic  compounds.  This  process  is  the  maximum  of 
synthetic  operation.  In  animals,  although  there  is  con- 
siderable synthesis,  analysis  predominates. 


4  PHYSIOLOGICAL    CHEMISTRY. 

CARBOHYDRATES. 

What  are  carbohydrates? 

Carbohydrates  are  organic  compounds,  forming  the  chief 
portion  of^the  dry  substance  ot  plants.  1  hey  occur,  in 
the  animal  kingdom,  in  proportionately  small  quantities, 
either  free  or  in  combination  with  more  complex  mole- 
cules, forming  compound  proteids,  as  gluco-proteids. 

Carbohydrates  contain  only  C,  H,  O,  the  latter  two 
elements  usually ""occurnng^in^e^  as  they 

^o  m  water^  viz.,  2 :  T7  hence  the  name  carbohydrates. 
They  are  readily  convertible  into  other  products,  yielding 
much  energy  and  heat. 

Hov^7  and  where  are  carbohydrates  derived  from  in- 
organic material? 

By  synthesis  in  the  chlorophyllic  bodies,  thus  : 

CO2  +  H2O  =  H.CHO  +  O2 
6H.CHO  =  C6Hi206  (dextrose). 

What  are  the  three  chief  groups  into  which  carbo- 
hydrates are  divided?    Give  examples  of  each  group. 

I.  Monosaccharides —  ,      ^ 

"  TDextrose  (glucose) .      «^ fc  ^ ' ^^  ^ ^ 

a.  Hexoses^  Levulose  (fruit-sugar). 
I  Galactose. 


{ 


1     Ti     ,  1  Arabinose. 


L.  w^^^„ 


2.  Disaccharides — 

Maltose. 

Lactose  (milk-sugar). 

Sucrose   (cane-sugar). 

3.  Polysaccharides — 

Starch.  . 

Dextrin.  ft         I4        ()  <- 

Glycogen  (animal  starch).  (p  ^0      '^ 

Cellulose. 


I 


6  PHYSIOLOGICAL    CHEMISTRY. 

What  are  the  general  qualitative  tests  for  carbohy- 
drates?   Describe  each. 

1.  Molisch's. 

2.  Plenylhydrazine. 

3.  Moore's. 

4.  Iodine. 

1.  Molisch's  Test. — To  the  sugar  solution  add  a  few 
drops  oi  alpha-naphthol,  then  cone.  H2SO4  in  excess.  A 
red  to  purple  color  will  result.  This  is  a  general  test 
for  all_  carbohydrates^  The  reaction  depends  upon  the 
forrnation  of  furKirol  from  the  sugar  by  the  H2SO4. 
The  furfurol  reacts  with  the  alpha-naphthol,  producing 
the  purple  zone. 

2.  Phenylhydrazine  Test. — To  the  sugar  solution  add  a  ^    <- 
spoonful  of  sodium  acetate  with  phenylhydrazine  hydro-  fl  O 
chloride.     Boil  and  allow  to  stand  24  hrs.     Characteristic 
crystals  will  form.    With  the  phenylhydrazine,  the  sugar 
first  yields  hydrazones,  with  the  elimination  of  H2O,  and 
upon  further  action,  osozones. 

Most  of  the  sugars  in  the  body  yield  crystals  with 
phenylhydrazine. 

3.  Moore's  Test. — Add  KOH  to  the  sugar  solution  and 
heat.  Yellow  color  results  with  a  faint  odor  of  caramel. 
This  is  a  test  for  dextrose  and  disaccharides. 

4.  iodme  'lest. — Most  "polysaccharides  added  to  an 
iodine  solution  turn  it  blue.  The  color  disappears  on 
warming  and  reappears  on  cooling. 

What  is  meant  by  the  "  inversion  of  sugars  "  ? 

By  ''  inversion  of  sugars "  is  meant  the  hydrolyti^ 
cleavag^e  of  compound  sugars  into  monosaccharides,  thus : 

Sucrose  +  HgO  =  Dextrose  +  Leyulose. 
Maltose  -j-  H2O  =  Dextrose  -|-  Dextrose. 
Lactose  -j-  H2O  =  Dextrose  -|-  Galactose. 

What  are  the  characteristics  of  monosaccharides? 

All  are  either  aldehydes  or  ketones  of  polyhydric  alco- 
hols and  are  termed  aldoses  and  ketoses  respectively,  thus  : 

Dextrose  =  CH2(OH).(CH(OH))4.CHO  =  aldose. 
Levulose  =  CH2(OH).(CH(OH))3.CO.CH2(OH)=ketose. 


u  ..i-^^  LL>dt3tv  6-^^  -  ^■^-'^^ 


PHYSIOLOGICAL    CHEMISTRY. 


All  are  strong  reducing  agents  due  to  the  aldehyde  or 
ketone  raciical  1  hey  are  colorless,  odorless,"  neutral  m 
reaction,  easily  soluble  in  HsQ^  difficultly  soluble  in  alco- 
hol and  insoluble  in  ether.  They  are  optically  active,  fer- 
mentable and  dittusible.  With  phenylhydrazine  they 
yield  characteristic  crystals. 


What  are  the  characteristics  of  disaccHarides  ? 

They  are  soluble  in  dilute  alcohol,  diffusible,  ferment- 
able and  have  reducing  powers.  With  phenylhydrazine, 
they  form  crystals.  They  do  not  respond  to  the  I  reac- 
tion (sucrose  is  an  exception  in  some  cases).  All  are 
converted'  into"  monosaccharides  by  hydrolytic  cleavage. 

What  are  the  characteristics  of  polysaccharides? 

Polysaccharides  are  characterized  by  general  insolu- 
bility. ( Glj^co^en  and  dextrin_  are_  soluble. )  Most  give 
the  I  color  reaction  or  yieH "products"wh"ich  y^ill.  They 
do  not  reduce,  are  indiffusible  and  non- fermentable  and  do 
not_  yield  crystals  y^ith  phenylhydrazine.  *"  Allare  ulti- 
mately converted  into  monosaccharides  by  hydrolytic 
cleavage. 

Write  reactions  to  show: 

1.  Synthesis    of    a    carbohydrate    from    inorganic 

radicals. 

CO2  +  H2O  =  H.CHO  +  O. 
6H.CHO  =  C6H,206 

2.  Production   of  a  polysaccharide  from  inorganic 

radicals. 

a.  6CO2  -f  6H2O  =  CeHi^Oe  -f-602 

b.  (CeHisOe  — HoO)x=  (C6Hio05)x+ (H20)x       x:=not    less 

than  5 

3.  Formation  of  CO2  from  glycogen. 

CeHxoOs  +  I2O  =  6CO2  +  SH2O 

4.  Inversion  of  a  disaccharide. 

C12H22O1X  +  H2O  =  CeHisOe  -f-  C9H12O6 


V  Q^t:uda  ^^ijy  ijOt^  <^^  ^ 

e.  H  0  H 
I 

•    C  W  0  H 


10  PHYSIOLOGICAL    CHEMISTRY. 

5.  Regeneration  of  a  polysaccharide  to  a  monosac- 

charide. 

a.  (CeHloOs)  X   +  H2O  =    (C6Hio05)2.H20  +    (C6Hio05)x-2 

b.  (CeHaoOs)  2.H2O  =  G2H22O11 

C.  Cl2i^ll  +  H2O  =  2C6H12O6 

6.  Formation  of  a  disaccharide  from  dextrose. 

2C6H12O6  —  H2O  =  C12H22O11  +  H2O 

7.  Formation  of  glycuronic  acid  from  dextrose. 

Dextrose  Glycuronic  Acid 

CH2OH  +  O      CHO 
(CH0H)4  =  (CHOH)4  +  H20 

CHO  +  O      COOH 


FATS. 

What  are  fats  chemically?    Name  the  three  chief  body 
fats.    Where  are  they  found  in  the  body? 

Fats  are  tri-glycerides,  being  composed  of  one  radicle 
of  glycerin  and  three  of  a  fatty  acid.  The  hydrogen  atoms 
of  the  three  hydroxyl  groups  are  each  replaced  by  a  fatty 
acid  radical. 

The  three  chief  fats  are  tri-stearin,  tri-palmatin  and  tri- 
olein. They  are  found  as  primary  constituents  of  every 
cell. 

What  are  the  leading  properties  of  fats?  fc. 

They  are  highly  refractive^  crystallize  in  rosettes,  and 
are  insoluble  in  all  the  common  reagents,  except  hot  alco- 
hol and  ether.  They  contain  a  small  amount  of  O  in 
proportion  to  C  and  H,  and  are  easilv  oxidized.  All  are 
saponifiable  and  relatively  indiffusible.  Tri-stearin  and 
tri-palmitin  are  solid,  tri-olein  liquid,  at  ordinary  tempera- 
ture.   Human  fat  is  75  per  cent,  tri-olein. 

State  the  more  important  facts  regarding  the  origin  of 
fat  from  proteids. 

1°.  The  putrefaction  of  proteid  material  is  accompanied 
by  the  formation  of  fatty  acids  and  glycerol. 


e  ^  u^^<i»<r<t«^ '  Mo,K 


TjU-,'^^Aft.l««-U 


't'OwU'. 


Stdfr  .uxoi^.  MMi"tXu 


12  PHYSIOLOGICAL   CHEMISTRY. 

2°.  Fresh  cheese  is  rich  in  proteids  but  contains  Httle 
fat.    As  it  ripens  the  amount  of  fat  is  increased. 

3°.  The  framework  of  animals,  rich  in  proteids,  some 
time  after  burial  may  be  converted  into  a  waxy  fat — adi- 
pocere.  The  muscle  proteids  are  thus  converted  into  salts 
of  the  fatty  acids. 

4°.  In  an  experiment  with  fly-maggots,  half  were 
killed  and  the  amount  of  fat  determined.  The  remainder 
were  allowed  to  develop  in  blood  whose  proportion  of  fat 
had  been  previously  determined.  These,  when  killed, 
were  found  to  contain  many  times  the  amount  of  fat  in 
the  maggots  first  analyzed  and  the  amount  in  the  blood 
together. 

5°.  Dogs  fed  upon  diet  containing  small  amounts  of 
fat  and  carbohydrate  and  much  proteid  material,  formed 
more  fat  than,  the  aggregate  in  the  fat  and  carbohydrate 
food. 

May  fat  arise  from  others  forms  of  food? 

It  may  arise  from  carbohydrate  and  fat  in  food.  Hence 
it  may  arise  from  all  three  classes  of  foods. 

What  is  meant  by  the  saponification  of  fats?     What 
products  are  formed?    Illustrate  by  formula. 

Saponification  is  a  process  of  hydration  in  which 
glycerol  and  free  fatty  acids  are  formed  from  the  fat. 
The  free  fatty  acid,  in  the  presence  of  an  alkali,  immedi- 
ately forms  a  salt — soap,  thus. 


G^HsxCOO- 

CH2      HO 

K 

G5H31COO- 

CH  +H0 

K  = 

C15H31COO  — 

CHa      HO 

K 

Palmitin 
(A  typical  fat) 

CH2  — OH 

I 
3CX5H31COOK  +  CH  —  OH 

CH2  — OH 

Potassium  palmitate  Glycerol 

(A  typical  soap) 


14  PHYSIOLOGICAL    CHEMISTRY. 

How  may  palmitic  acid  be  prepared?  Give  its  leading 
properties. 

Heat  some  Bayberry  tallow  in  water  and  saponify  with 
some  KOH.  (Alcohol  favors  the  reaction.)  Add  HCL 
till  the  solution  is  distinctly  acid.  Cool.  Free  palmitic 
acid  appears  on  the  surface  and  hardens.  To  remove 
impurities,  the  cake  of  palmitic  acid  is  removed  and  re- 
dissolved  in  warm  alcohol.  Upon  cooling,  crystals  of  pure 
palmitic  acid  separate  out. 

Properties. — It  is  solid  at  ordinary  temperatures,  and 
is  insoluble  in  the  common  reagents  except  ether  and 
warm  alcohol.  It  is  highly  refractive  and  crystallizes 
in  rosettes. 

How  may  glycerin  be  prepared?  Mention  its  leading 
properties. 

Proceed  as  above.  The  residue  from  which  the  cake  of 
crude  palmitic  acid  is  abstracted,  contains  the  glycerin. 
The  solution  is  acid  due  to  HCl.  Neutralize.  (Acid 
destroys  the  glycerin.)  Set  in  the  hood  for  evaporation. 
The  water  evaporates  and  glycerin  and  KCl  remain.  Ex- 
tract the  glycerin  with  95  per  cent,  alcohol.  Filter. 
Evaporate  the  filtrate  on  the  water  bath.  Alcohol  evap- 
orates and  glycerin  remains. 

Properties. — It  is  a  heavy,  colorless  liquid,  soluble  in 
all  the  common  reagents,  except  ether.  It  has  a  solvent 
action  on  oxides  and  hydroxides  of  certain  metals  and 
responds  to  the  acrolein  test. 

(a)  Describe  the  acrolein  test.  (&)  Write  the  reaction 
involved,  {c)  Name  the  substances  that  will  respond 
to  the  test. 

This  is  a  characteristic  test  for  glycerin  radicals  in  fats. 
Add  a  few  crystals  of  K  bi-sulphate  (KHSO4)  to  the 
suspected  substance.  Heat.  The  odor  of  burning  tallow 
indicates  the  presence  of  glycerin. 

CH2OH  CHo 

I  I 

(h)  CHOH— 2H20  =  CH 

CH2OH  CHO 

(acrolein  or  acrylic  aldehyde) 


l6  PHYSIOLOGICAL    CHEMISTRY. 


(c)   Neutral  fats  ^ 
Lecithin 
Cerebrin 
Glycerin 


^Due  to  glycerin  radicals. 
PROTEIDS.  fi  ^ 


?^ 


What  are  proteids?     Where  are  they  found  in  the 
body? 

Proteids  are  complex  nitrogenous  substances,  contain- 
ing C,  O,  H,  N,  S  and  sometimes  P,  Fe  and  other  metals. 
The  N  constitutes  about  i6  per  cent,  and  with  few  ex- 
ceptions is  capable  of  being  utilized  by  the  body. 

Proteids  are  the  groundwork  of  all  forms  of  living 
matter  and  are  primary  constituents  of  every  cell.  Upon 
decomposition,  they  yield  the  hexon  bases  (histidin,  lysin 
and  arginin). 

Give  the  classification  of  proteids.    Upon  what  is  this 
classification  based? 

1.  Simple  proteids — 

Albumins. 

Globulins. 

Coagulated  proteids. 

Albuminates. 

Proteoses. 

Peptones. 

2.  Compound  proteids — 

Nucleo-proteids. 

Chromo-proteids. 

Gluco-proteids. 

3.  Albuminoids   or  Albumoids — 

Collagen. 

Gelatin. 

Elastin. 

Keratin. 
This  classification  is  based  upon  solubilities  and  decom- 
position products.    Of  the  inner  character  of  proteids  but 
little  is  known. 


1 8  PHYSIOLOGICAL    CHEMISTRY. 

Describe  each  and  tell  where  found. 

The  simple  proteids  are  never  failing  constituents  of  the 
animal  and  vegetable  organisms.  Albumins  and  globu- 
lins are  called  "  native  "  simple  proteids.  They  are  simi- 
lar, differing  chiefly  in  solubilities.  Coagulated  proteids 
occur  in  certain  organs  as  the  liver  but  are  chiefly  promi- 
nent in  dead  muscle  and  fibrin  of  drawn  blood. 

Albuminates  are  derived  from  the  native  proteids  by 
the  action  of  acids  or  alkalies.  The  concentrated  ''  alkali  " 
albuminate,  formed  by  the  action  of  strong  KOH  on  ^gg 
albumin,  is  known  as  Lieberkilhn's  Jelly. 

Proteoses  and  peptones  are  digestive  products  from 
proteids,  resulting  from  the  action  of  proteolytic  enzymes. 
Both  are  very  simple  proteids. 

The  compound  proteids  are  compounds  of  simple  pro- 
teids with  radicals  that  are  not  proteids.  Nucleo-proteids 
are  widely  diffused  in  the  animal  body.  They  occur  chiefly 
in  cell  nuclei  but  frequently  in  protoplasm.  Chromo- 
proteids  occur  in  various  cells.  Their  chief  representation 
is  the  red  pigment,  hemaglobin.  Gluco- proteids  are  im- 
portant constituents  of  all  connective  tissue.  Upon  de- 
composition, they  yield  a  proteid  and  a  carbohydrate. 

Albuminoids  are  very  similar  in  certain  respects  to  al- 
bumins. They  are  formed  only  in  animal  tissue,  and 
seem  to  be  modified  from  the  albumin  and  globulin  of 
cells.  Collagen  is  the  chief  constituent  of  the  fibrils  of 
connective  tissue  and  of  the  organic  substance  (ossein) 
of  bone.  Upon  boiling  it  is  converted  into  gelatin.  The 
chief  constituent  of  elastic  tissue  is  elastin.  Keratin  is  the 
supporting  element  in  epidermal  tissue,  brain  and  nerves. 

What  are  the  three  general  color  reactions  for  pro- 
teids?    Describe  and  explain  each. 

Biuret. 

TMtillon's. 

Xanthoproteic. 

Biuret. — To  a  proteid  solution,  made  distinctly  alka- 
line with  KOH,  add  a  very  dilute  CuSO^  solution.  A 
reddish  violet  color  results. 

This  color  results  from  a  change  in  the  Cu  compound 
due  to  the  Biuret  radical  in  the  proteid. 


/ 


atit^it0<»mm'nim!09t  mtn 


20 


PHYSIOLOGICAL    CHEMISTRY. 


Millon's  Reaction. — Treat  the  proteid  with  Millon's 
reagent  (solution  of  Hg  in  HNO3  and  HNO2).  A  white 
precipitate  is  formed  which  turns  red  upon  warming. 

This  reaction  is  due  to  the  phenol  group,  CgHgOH,  in 
the  proteids.  Other  substances  than  proteids,  containing 
the  phenol  radical,  respond  to  the  test.  Thus  tyrosin, 
found  in  intestinal  digestion,  gives  a  red  coloration ."^Thls 
is  Hofmann's  reaction. 

Xanthoproteic  Test. — Add  concentrated  HNO3,  in  ex- 
cess, to  the  proteid  solution.  Heat  until  a  distinct  canary 
yellow  color  appears.  Cool.  Then  add  NH^OH  in  ex- 
cess.    An  orange  color  results. 

The  HNO3  precipitates  the  proteid,  which  precipitate 
dissolves  in  an  excess  of  the  acid.  Upon  warming, 
xanthoproteic  acid  is  formed  (canary  yellow).  The  am- 
monia compound  of  this  acid  furnishes  the  orange  colora- 
tion. The  reaction  depends  upon  the  benzene  radical, 
QHg,  in  the  proteid. 

In  these  color  reactions  the  character  of  the  proteid 
molecule  is  unchanged. 


Give  a  table  of  the  solubility  of  proteids  in  the 
mon  '*  reagents. 


com- 


■* 

0^ 
X 

0 

g  1 

a 

! 

3  t; 

Albumin. 

s. 

s. 

s. 

P. 

p. 

N. 

c. 

Globulin. 

I. 

s. 

s. 

p. 

p. 

N. 

c. 

Albuminates. 

I. 

I. 

s. 

p. 

p. 

N. 

c* 

Proteoses. 

s. 

s. 

s. 

p. 

p. 

D. 

N. 

Peptones. 

s. 

s. 

s. 

N. 

p? 

D. 

N. 

Coagulated  Proteids. 

1. 

I. 

I. 

N. 

S  ^  Soluble 
I  =■  Insoluble 
P  =  Precipitate 
C  =:  Coagulable 
D  =  Diffusible 
N  =  Negative 


*  In  neutral  solutions. 


22  PHYSIOLOGICAL    CHEMISTRY. 

How  may  proteids  be  precipitated  from  their  solutions? 

a.  By  the  addition  of  single  reagents,  as : 

1°.  Neutral  salts,  such  as  (NH4)2S04  to  satura- 
tion. This  precipitates  all  proteids  except 
peptones. 

12°.  Metallic  salts  of  Hg,  Cu,  Pb,  to  saturation. 
Hence  the  use  of  egg-albumin  as  an'  anti- 
dote in  poisoning  by  metallic  salts. 
3°.  Alcohol  or  ether,  in  excess,  to  faintly  acidu- 
lated proteid  solutions.  All  proteids  are 
precipitated. 
j  4°.  The  three  mineral  acids,  HCL,  H2SO4,  HNO3, 
at  ordinary  temperatures. 

b.  By  the  addition  of  paired  reagents  : 
1°.  Acetic   acid   -j- K   ferro-cyanide.      This   is   a 

delicate  test  for  albumin  in  urine. 
2°.  HCL  -j-  K  mercuric  iodide. 

c.  By  the  addition  of  alkaloidal  reagents,  as : 

1°.  Tannic   acid,    in   acetic   acid   solution.      This 

precipitates  all  proteids. 
2°.  Phosphotungstic   acid,   in   the   presence   of   a 

free  mineral  acid. 
3°.  Picric  acid,  in  the  presence  of  an  organic  acid. 

How  would  you  prepare  a  globulin?     Give  its  leading 
properties. 

Globulin  may  be  prepared  from  hemp  seed  by  warming 
the  seed  in  a  5  per  cent.  NaCl  solution.  Filter  while 
warm.  Upon  cooling  a  deposit  forms  in  the  filtrate.  This 
deposit  is  a  vegetable  globulin,  edestin,  and  may  be  sep- 
arated from  the  solution  by  filtration. 

Properties. — It  is  insoluble  in  water  but  soluble  in  the 
other  reagents  dissolving  albumin.  Under  the  micro- 
scope it  shows  a  crystalline  character.  It  responds  to  the 
three  color  reactions  for  proteids. 

What  are  albuminates? 

They  are  derived  albumins,  produced  by  the  action  of 
acid,   alkali   or   certain   salts   on   albumins   or   globulins. 


24  PHYSIOLOGICAL    CHEMISTRY. 

This  results  in  the  splitting  off  of  a  little  HgS  and  NHg. 
The  more  common  forms  are  acid  or  alkali  albuminates. 

How  may  an  albuminate  be  precipitated? 

To  a  solution  of  albumin  add  a  few  drops  of  an  acid 
or  alkali  and  boil.  An  albuminate  is  formed  but  no 
precipitation  results  due  to  the  alkalinity  or  acidity  of 
the  solution,  in  which  albuminates  are  soluble.  Upon 
neutralizing,  the  albuminate  is  precipitated.  Albumins 
heated  in  a  neutral  solution  coagulate.  If  heated  in  an 
acid  or  alkaline  solution  no  coagulation  occurs. 

How  may  nucleo-proteid  be  prepared?     Give  its  chief 
properties. 

Nucleo-proteid  may  be  prepared  from  yeast  cells  by 
grinding  yeast  with  water  and  sand,  thus  rupturing  the 
cells  and  making  them  more  permeable  to  extraction 
through  exposure  of  their  nuclei.  Transfer  the  ground 
mass  to  a  small  beaker  of  water  and  allow  to  stand  30 
minutes.  Filter.  Treat  the  residue  with  .5  per  cent. 
KOH.  (Nucleo-proteids  are  soluble  in  dilute  alkali.) 
Filter.  To  the  filtrate  add  dilute  HNO3.  A  flocculent 
precipitate  of  nucleo-proteid  appears. 

Properties. — It  is  insoluble  in  H2O  and  NaCl  solution 
but  readily  soluble  in  dilute  KOH.  Nucleo-proteids 
contain  a  high  percentage  of  P  and,  upon  decomposition, 
are  characterized  by  yielding  purin  bases  in  addition  to 
phosphoric  acid  and  carbohydrate,  thus : 

Nucleo-proteid 

/  \ 

Proteid  Nuclein 


Proteid      Nucleic  acid 

/         I         \ 
Purin  bases     H3PO4     Carbohydrate 

How  may  a  nucleo-proteid  be  differentiated  from  any 
other  proteid?    Describe  the  test. 

True  nucleo-proteids,  upon  decomposition,  yield  purin 
bases.    Other  proteids  do  not. 

Test  for  Purin  Bases. — Make  the  solution  to  be  tested 
alkaline.  Then  add  to  it  an  ammoniacal  solution  of 
AgNOg.  Purin  bases  will  be  precipitated  as  a  brown 
flocculent  precipitate. 


U,.^<X^^A      fMJUk 


26  PHYSIOLOGICAL    CHEMISTRY. 

THE    CELL. 

Distinguish  between  primary  and  secondary  cell  con- 
stituents. Name  the  primary  and  give  three  typical 
examples  of  secondary  constituents. 

Primary  constituents  are  those  which  are  present  in  all 
cells  and  are  essentially  necessary  for  the  life  of  the  cells. 
Secondary  constituents  are  those  which  are  casual,  stored 
up  as  reserve  material  or  as  metabolic  products  and  differ- 
entiate one  cell  from  another. 

PRIMARY  CONSTITUENTS. 

r  Nucleo-Proteids   (True,  Pseudo) 
1°  Proteids  <  Albumin 

I  Globulin 

."Carbohydrates         {  g^^^f " 

r  Simple  fats 

3°  Fats  <  Lecithin 

L  Cholesterin 

f  FT  O 
4°  Inorganic  material  \  c  V^ 

SECONDARY  CONSTITUENTS. 
1°  Enzymes. 
2°  Pigment. 
3°  Fat    (in   adipose  tissue). 

Describe  methods  for  the  separation  from  egg  yolk  of 
lecithin,  cholesterin  and  fat. 

To  egg  yolk  add  25  c.c.  ether  and  a  small  beaker 
of  alcohol.  Shake  well  and  allow  to  stand.  The  fats 
and  inorganic  material  dissolve.  Filter.  The  yellow- 
ish precipitate  is  proteid  matter  (nucleo-proteid,  albumin 
and  globulin),  and  the  filtrate  contains  the  fat  and  inor- 
ganic material. 

Evaporate  the  filtrate  to  dryness  and  extract  with  ether. 
To  this  ether  extract  containing  fat,  lecithin,  cholesterin 
and  lipochrome,  add  50  c.c.  of  acetone.  This  precipitates 
the  lecithin.    Filter.    Precipitate'"is  lecithin. 

Filtrate. — Evaporate  to  dryness.  (Contains  cholesterin, 
fat  and  pigment.)    The  cholesterin  may  be  separated  from 


28  PHYSIOLOGICAL    CHEMISTRY. 

the  fat  by  destroying  the  latter  without  affecting  the 
cholesterin.  This  is  accompHshed  by  saponifying  the  fat. 
Treat  the  mixture  with  5  c.c.  of  alcohol  and  5  c.c.  KOH 
and  boil.  Evaporate  to  dryness.  Add  water  and  two 
spoonfuls  of  NaCl.  Stir  thoroughly.  This  forms  Na 
soap  which  is  less  soluble  than  K  soap.  Evaporate  to 
dryness  and  extract  with  ether.  The  cholesterin  dissolves 
in  it  but  the  soap  and  NaCl  do  not.  Filter.  The  choles- 
terin remains  in  the  filtrate  and  crystallizes  out  upon 
evaporation.  The  fat  is  left  in  the  precipitate  in  the  form 
of  Na  soap. 

Describe  lecithin. 

Lecithins  are  complex  phosphorized  fats  and  are  essen- 
tial constituents  of  every  cell.  In  physical  properties 
they  resemble  fats.  They  are  soluble  in  alcohol  and  ether 
and  are  precipitated  by  acetone;  in  water  they  swell  to  a 
pasty  mass  and  show,  under  the  microscope,  slimy,  oily 
threads  and  drops,  so-called  myeline  forms.  From  the 
structural  formula  of  a  typical  lecithin, 

C17H35COO  — CH, 

I 
CitHsbCOO  — CH 

I  1 

^O  — CH2  — CH2  xf^  r, 

(CH3)3  =  N  — OH 

it  is  seen  that  di-stearyl  lecithin  is  stearin  with  one  fatty 
acid  radical  replaced  by  the  cholin-phosphate  group.  It 
follows  from  the  formula  that  lecithin  will  respond  to  the 
acrolein  reaction  due  to  the  glycerin  radical  and  upon 
decomposition  show  the  presence  of  P,  N  and  fatty  acids. 

Give  the  characteristics  of  cholesterin  and  describe  two 
typical  tests  for  it. 

Cholesterin  is  similar  to  fat,  and  therefore  insoluble 
in  the  usual  reagents.  It  is  soluble  in  ether,  chloroform 
and  warm  alcohol,  from  which,  upon  evaporation,  it 
yields  characteristic  crystals. 


H"f>  -  (M^t.  -  '^  ''I 


^3-     »  U 


,iL.iA^  "  *'^-^ 


d^  fc 


30  PHYSIOLOGICAL    CHEMISTRY. 

Salkowski's  Reaction. — Dissolve  the  solid  cholesterin  in 
chloroform.  Add  an  equal  volume  concentrated  H2SO4. 
Shake  thoroughly.  The  solution  becomes  a  cherry  red 
which  gradually  deepens  in  color. 

Cholesterin  I odine  Test. — Place  a  cholesterin  crystal  on 
a  microscope  slide  and  add  a  drop  of  tincture  of  iodine. 
Put  on  the  cover  slide  and  allow  a  drop  of  H2SO4  to  ooze 
under.  A  series  of  colors,  from  brown  through  green  to 
blue,  will  follow  the  line  of  advance  of  the  acid. 


CHEMISTRY    OF    THE    TISSUES. 
What  are  the  characteristics  of  tendon? 

Tendon  is  a  form  of  connective  tissue  whose  chief  con- 
stituent (one-third)  is  collagen.  It  contains  little  lymph 
and  blood  and  has  a  passive  mechanical  function,  being 
best  adapted  for  weight  and  strength. 

Describe  collagen. 

Collagen  is  an  albuminoid,  characterized  by  its  tensile 
strength.  Although  it  is  very  insoluble  it  is  easily  hy- 
drated,  in  warm  water,  to  gelatin.  Thus  the  collagen  in 
tissues  is  quantitatively  estimated  by  the  amount  of  gelatin 
it  yields.  Upon  being  heated  in  acid,  it  swells  up  and, 
upon  decomposition,  shows  the  presence  of  S.  It  is  di- 
gestible due  to  the  fact  that  it  is  easily  hydrated. 

Describe  mucoid.    How  may  it  be  prepared? 

Mucoid  is  a  constituent  of  all  forms  of  connective  tissue, 
especially  tendon.  It  is  a  compound  proteid,  gluco; 
£roteid,  being  composed  of  a  proteid  and  a  sugar-like 
radical.  Upon  decomposition  by  acid  it  yields  H2SO4 
instead  of  H3PO4  and  no  purin  bases,  thus  :  ' ' 

Gluco-proteid 

Proteid  Chondroitin  H2SO4 

/  \ 

Chondroitjn  H2SO4 

/      \ 

Chondroisin  Fatty  acid  (acetic) 

/  \ 

Glucos-amine        Glycuronic  acid. 


cuiiujibU^  9mMj^^ 


32  PHYSIOLOGICAL    CHEMISTRY. 

Preparation. — It  may  be  extracted  by  dilute  alkali,  as 
lime-water,  and  precipitat^dTb^^^acid. 

Where  does  elastin  occur?    How  may  it  be  extracted? 
Give  its  properties. 

Elastin  occurs  in  the  connective  tissues  of  higher  ani- 
mals, sometimes  in  such  quantities  that  it  forms  a  special 
tissue.     Ligamentum  nuchge  is  one-third  elastin. 

Extraction. — With  water,  wash  the  ligament  free  of 
blood.  Put  it  in  a  dilute  lime-water  solution  to  dissolve 
out  the  mucoid.  Then  boil  the  ligament  and  filter  while 
hot.     Elastin  remains  on  the  filter  paper. 

Properties. — It  is  insoluble  in  the  usual  reagents  and 
is  generally  considered  as  a  sulphur-free  substance.  It 
permits  of  great  stretching.  In  tendon,  over-stretching 
is  prevented  by  the  collagen. 

What  is  the  chief  constituent  of  epidermal  tissue? 

Keratin. — It  is  a  condensation  product  of  albumins  and 
globulins,  being  derived  from  the  underlying  cells.  It  is 
the  chief  constituent  of  the  horny  substance  of  the  epi- 
dermis, hair,  nails,  hoofs  and  horns,  and  also  occurs  as 
neurokeratin  in  the  brain  and  nerves.  It  is  insoluble, 
being  the  most  resistant  of  all  organic  material  and  is  of 
no  food  value.  When  heated  in  a  strong  acid  or  alkali 
it  will  decompose.  It  is  characterized  by  containing  a 
large  percentage  of  loosely  combined  S. 

How  would  you  detect  the  presence  of  S  in  keratin? 

Decompose  the  keratin  by  boiling  it  in  KOH.  This 
liberates  the  S.  Add  a  few  drops  of  Pb  acetate.  A  dark 
brown  color  results  from  the  formation  of  Pb  sulphide. 

Describe  osseous  tissue. 

Bone  is  a  peculiar  connective  tissue,  being  characterized 
by  great  rigidity.  It  consists  of  an  organic  matrix  im- 
pregnated with  lime  salts.  If  treated  with  dilute  HCl, 
the  inorganic  substances  are  dissolved  and  the  organic 
material  remains  as  a  soft,  elastic  mass,  preserving  the 
original  shape  of  the  bone.    This  organic  matrix  consists 


34  PHYSIOLOGICAL    CHEMISTRY. 

chiefly  of  ossein,  a  substance  practically  identical  with 
collagen.    It  also  contains  mucoid  and  albuminoid. 

After  complete  calcination  of  the  organic  substance,  a 
white,  brittle  mass  remains.  This  represents  the  inorganic 
constituents  which  in  some  cases  amount  to  50  per  cent, 
of  the  solid  material. 

Bone  is  comparatively  poorly  supplied  with  blood- 
vessels and  must  be  ranked  with  the  chemically  passive 
tissues. 

What  are  the  chief  inorganic  constituents  of  bone? 

Ca,  Mg,  Na,  K,  Fe. 
P2O5,  CI,  CO2. 

Ca3(P04)2  predominates.  Traces  of  sulphates  and 
silicates  may  occur. 

Describe  cartilage. 

Cartilage  is  in  some  respects  similar  to  tendon,  in  others 
to  bone.  Like  tendon  it  contains  a  large  amount  of  col- 
lagen. It  differs  from  bone  chiefly  in  the  amount  of 
inorganic  constituents.  It  is  characterized  by  its  content 
of  chondroitin-sulphuric  acid,  uncombined  with  proteid, 
in  the  form  of  a  Na  or  K  salt.  Its  mucoid  is  spoken  of 
as  chondro-mucoid. 

Describe  muscle. 

Muscle  is  composed  of  fibers  (cells)  bound  together 
with  little  intercellular  substance.  Each  fiber  consists  of 
a  sheath,  sarcolemma,  composed  of  a  substance  analogous 
to  elastin,  and  enclosing  a  homogeneous,  semi-fluid  sub- 
stance. Upon  death,  this  viscid  content  solidifies  (rigor 
mortis).  Muscle  has  an  abundant  blood  and  lymph  sup- 
ply and  ranks  as  one  of  the  most  active  tissues. 

What  are  the  chief  constituents  of  muscle? 

Muscle  contains  about  75  per  cent,  water,  18  per  cent, 
proteid,  3  per  cent,  fat,  3  per  cent,  inorganic  salts,  2  per 
cent;  collagen,  .2  per  cent,  extractives,  and  traces  of  gly- 
cogen. 


\hjAilh.--' 


^'^^-V'"'*'*'^ 


7,6  PHYSIOLOGICAL    CHEMISTRY. 

Describe  the  chief  muscle  proteids. 

Like  blood  which  contains  a  fluid  (blood  plasma),  which 
spontaneously  coagulates,  separating  fibrin  and  yielding 
blood  serum,  so  living  muscle  has  a  coagulating  liquid 
(muscle  plasma)  which  spontaneously  coagulates,  separat- 
ing a  clot,  myosin  (myosin  fibrin)  and  also  a  serum.  This 
coagulating  process  occurs  soon  after  death,  in  rigor 
mortis,  and  is  probably  due  to  an  enzyme.  This  myosin  is 
a  post-mortem  product  and  is  never  present  in  living 
muscle.  Its  antecedents  are  myosinogen  and  para-myo- 
sinogen.  Myosin  is  a  globulin,  constituting  about  7  per 
cent,  of  the  dead  muscle ;  it  is  soluble  in  10  per  cent.  NaCl 
but  is  precipitated  upon  saturation. 

Concerning  the  stroma  substance  but  little  is  known. 
It  is  insoluble  in  NaCl  but  soluble  in  dilute  alkalies  in 
which  it  is  transformed  into  albuminate.  The  elementary 
composition  is  nearly  the  same  as  that  of  myosin. 

What  can  you  say  of  the  presence  and  significance  of 
the  inorganic  salts  and  fat  in  muscle? 

The  predominating  inorganic  constituents  are  K  and 
phosphoric  acid.  Next  in  amounts  are  Na  and  Mg; 
traces  of  Ca,  Fe  and  CI  are  also  present.  It  appears  that 
the  combined  action  of  these  ions  is  necessary  for  the 
normal  function  of  the  muscle. 

Fat  is  present  in  variable  quantities,  both  as  inter- 
muscular and  intra-muscular  fat.  The  latter  is  within 
the  sarcolemma  and,  due  to  its  high  calorific  power,  is 
the  best  form  of  potential  energy  the  body  has. 

What  is  the  carbohydrate  in  muscle?  Describe  it. 
How  does  it  get  to  the  muscle?  What  results  from 
its  breaking  down? 

Glycogen  and  glucose,  into  which  it  is  transformed. 

Glycogen,  first  called  animal  starch,  resembles  vegetable 
starch  in  its  physical  and  chemical  characteristics,  differ- 
ing chiefly  in  its  coloration  with  I,  giving  a  brownish-red 
color,  and  in  being  very  soluble  in  water,  producing  a 
characteristic  opalescence. 

Glycogen  reaches  muscle  as  sugar  or  as  glycogen,  itself, 


5u1^4jua 


m 


38  PHYSIOLOGICAL    CHEMISTRY. 

coming   from   the   liver   where   it   is   manufactured   and 
stored.    It  is  the  leading  fuel  material  of  muscle. 
CO2  and  H2O  result  from  its  breaking  down. 

How  may  glycogen  be  extracted  from  muscle?     Give 
its  properties. 

Glycogen  is  present  in  all  muscles  but  only  in  traces. 
It  is  most  easily  extracted  from  scallops  which  are  practi- 
cally all  muscle  and  contain  much  glycogen  . 

Extraction. — Grind  scallops  with  sand  and  place  in 
casserole  with  water.  Heat  and  stir  constantly  till  boil- 
ing. Then  add  a  few  drops  of  acetic  acid  to  coagulate 
any  proteid  not  already  coagulated.  Filter.  The  filtrate 
is  milky,  due  to  suspended  glycogen.  Add  alcohol  and 
a  white  flocculent  precipitate  of  glycogen  will  appear. 

Properties. — It  is  soluble  in  all  the  reagents  except 
alcohol  and  ether,  and,  therefore,  is  soluble  in  all  the  body 
fluids.  Its  aqueous  solution  is  characterized  by  opal- 
escence (Ex.  =  clam  broth).  It  is  readily  converted  into 
sugar  and  easily  oxidized  to  CO2  and  H2O. 

What  are  the  chief  extractives?    Why  is  it  important 
to  know  about  these? 

The  extractives  are  creatin,  creatinin,  xanthin,  hypO- 
xanthin,  guanin,  and  carnine.  They  are  important  be- 
cause they  represent  products  of  the  changes  which  pro- 
teid material  is  undergoing. 

How  would  you  obtain  these  extractives  from  muscle? 

Stir  some  hashed  beef  in  a  NaCl  solution  and  allow  to 
stand.  Filter.  Saturate  the  filtrate  with  NaCl.  The  floc- 
culent precipitate  ^  m3/06-w.  Filter.  The  filtrate  con- 
tains all  the  extractives  and  the  inorganic  matter.  To  get 
rid  of  the  inorganic  radicles,  add  Pb  acetate.  The  precipi- 
tate ^PbSO^,  Pb3(P04)2  and  PbCl2.  Filter.  H2S  is 
run  through  to  precipitate  the  Pb  which  is  filtered  off, 
leaving  the  extractives  in  solution. 


hjj^ 


40  PHYSIOLOGICAL    CHEMISTRY. 

What  are  purin  bases?    Illustrate  by  formulae. 

Purin  bases  are  modifications  of  a  compound, 
N  =  CH 

!       I 

CgH-N,  orHC     C  — NH. 

II        II  >H 

N  — C  — N   ^ 
called  purin. 

The  different  purin  bases  are  derived  from  purin  by  the 
substitution  of  the  various  H  atoms  by  hydroxyl  or  other 
groups.  In  order  to  signify  the  different  positions  of 
substitution,  the  nine  members  of  the  purin  nucleus  have 
been  numbered  thus : 

3N-C,-N/ 
Thus  xanthin,  2,  6 — di-oxypurin  is 
HN  —  CO 
CO        C  — NH. 

I         II  Vh 

HN  — C  — N   ^ 
Hypoxanthin,  6 — oxypurin  is 
HN  —  CO 
HC        C  —  NH 


.1  ,.  )CH 

N C  — N   ^ 

Uric  acid,  2,  6,  8 — trioxypurin  is 
HN  — CO 
CO        C  —  NH. 

I         II  >co 

HN  — C  — NH^ 

It  is  believed  these  purin  bases  are  oxidized  to  uric  acid 
and  excreted  as  such. 


(jkiM^^ 


42  PHYSIOLOGICAL    CHEMISTRY. 

How  may  creatin  be  separated  from  the  purin  bases? 

With  88  per  cent,  alcohol  which  dissolves  the  purin 
bases  without  affecting  the  creatin. 

What  is  creatin?    Illustrate  by  formula. 

Creatin  is  a  nitrogenous  body,  methyl-guanidin-acetic 
acid,  formed  in  muscle  as  a  wear-and-tear  product.  It 
is  closely  related  to  creatinin  which  is  creatin,  dehydrated. 
Creatin  is  similar  to  urea,  thus : 

Urea.  Guanidin  or  imino  urea. 

/NH2  /NH2 

I.         0=C<  II.      NH3^C< 

\nH2  \NH2 

III.  Methyl  guanidin, 

NH, 
NH  =  C< 

\NH(CH)3 

IV.  Methyl-guanidin-acetic  acid --=  creatin. 


NH, 

NH=:C< 

\n(ch3; 


Creatin  by  dehydration  =  creatinin,  thus  : 

/NH, 
NH=C<(  /NH- 

\N  (CH3)  CH2COOH— H20=NH=C<  I 

\N(CH3)CH2CO 

In  the  urine,  it  appears  as  creatinin. 
What  is  the  reaction  for  creatinin?    Describe  it. 

Weyl's  Reaction. — Make  the  creatinin  solution  alkaline 
with  KOH.  Add  a  drop  of  Na  nitro-prussid.  A  red 
color  results  which  is  destroyed  by  acidification.  Acetone 
responds  to  the  test  but  the  color  does  not  disappear  upon 
acidification  (Legal's  test). 

What  is  the  food  value  of  commercial  meat  extract? 

The  extracts  contain  practically  no  proteid  or  fat,  and 
but  little  carbohydrate.  Hence,  since  food  material,  which 
yields  energy,  is  mainly  composed  of  proteid  fat  and  car- 


^fUKUA 


44  PHYSIOLOGICAL    CHEMISTRY. 

bohydrate,  the  extracts  have  no  real  food  value.  But 
they  are  medicinally  valuable  due  to  their  contents  of 
purin  bases  and  inorganic  salts,  both  of  which  serve  as 
stimulants.  The  K  salts  are  especially  valuable  as  a  heart 
stimulant.  Meat,  extracted  in  cold  solution,  would  be 
of  real  food  value  as  the  extract  would  contain  the 
three  food  stuffs. 

What  is  the  reaction  of  living  muscle,   (a)   at  rest? 
(b)  after  work?    Explain  these  phenomena. 

The  reaction  at  rest  is  alkaline  due  to  K2HPO4  the 
predominating  salt;  after  work  it  is  acid. 

During  the  breaking  down  of  glycogen,  synchronous 
with  muscular  activity,  lactic  acid  is  formed.  This  im- 
mediately reacts  with  the  alkaline  phosphate  K2HPO4 
transforming  it  into  acid  phosphate  H2KPO4  by  with- 
drawing basic  ions  for  its  own  neutralization.  That  the 
acidity  is  due  to  acid  salts  and  not  free  lactic  acid,  may 
be  shown  with  lachmoid  paper  which  does  not  change 
color  except  with  free  acids. 

Describe  nerve  tissue. 

Nerve  tissue  consists  largely  of  connective  tissue  ele- 
ments which  hold  nerve  cells  and  their  processes.  It 
contains,  besides  the  general  primary  constituents,  cer- 
tain highly  specialized  fatty  substances,  as  cerebrin,  choles- 
terin,  lecithin,  and  protagon.  The  supporting  proteid 
is  neuro-keratin.  These  various  constituents  exist  in  the 
brain  in  loose  molecular  combination,  and,  it  is  believed, 
each  mental  propagation  is  due  to  a  physical  or  molecular 
change  in  these. 

How  would  you  separate  lecithin,  cholesterin  and  cere- 
brin from  brain  tissue?    Describe  cerebrin. 

Put  the  hashed  brain  in  cold  alcohol.  This  extracts 
the  lecithin.  (A  small  amount  of  cholesterin  usually 
accompanies.)  Upon  evaporating  the  cold  alcohol  ex- 
tract, lecithin  will  remain. 

Cholesterin  is  best  extracted  with  cold  ether.  Beauti- 
ful crystals  appear  upon  evaporation. 


rt>(rf"flL4't 


U  SA 


46  PHYSIOLOGICAL    CHEMISTRY. 

Cerebrin  may  be  obtained  from  brain  tissue  from  which 
the  lecithin  and  cholesterin  have  been  removed,  by  heating 
it  with  95  per  cent,  alcohol.  It  separates  out  and  goes 
into  solution  in  the  hot  alcohol. 

Cerebrin  is  a  N  substance,  free  from  P,  and  similar 
in  physical  properties  to  cholesterin.  Like  the  fats,  it 
is  soluble  in  warm  alcohol  and  chloroform,  but  differs  in 
being  insoluble  in  cold  alcohol  and  ether.  It  contains  a 
sugar-like  radical  and,  upon  decomposition,  yields  a  fat 
and  a  carbohydrate  (galactose). 

Indicate  (a)  the  composition  of  liver;  (b)  its  functions. 

Liver,  like  muscle,  is  about  three-fourths  water.  Of 
the  solids,  9  per  cent,  is  proteid,  3  per  cent,  fat,  glycogen 
in  variable  amounts  and  5  per  cent,  extractives.  It  also 
contains  ferratin  (iron  albuminate). 

The  most  important  functions  are : 

1.  Manufacture  of  bile. 

2.  Manufacture  and  storage  of  glycogen. 

3.  Formation  of  urea^, 

4.  Filtration  and  storing  of  heavy  metals  and  albu- 
minoids. 

Hov^r  may  iron  albuminate  be  prepared  from  liver? 
What  is  peculiar  about  the  iron  in  that  substance? 

Grind  some  hashed  liver  with  sand.  Transfer  it  to  a 
casserole,  one-half  full  of  water,  and  gradually  heat  to 
boiling.  This  coagulates  all  the  proteids  except  iron 
albuminate  which  is  not  coagulated  by  heat.  Filter.  The 
filtrate  contains  iron  albuminate,  glycogen  and  the  ex- 
tractives. Acidify  with  tartaric  acid  and  a  flocculent  pre- 
cipitate of  iron  albuminafe^wiir  fall. 

The  iron  in  this  albuminate  (ferratin)  is  closely  com- 
bined with  the  proteid.  It  is  so  intimately  combined 
with  the  proteid  radical  that  it  will  not  respond  to  iron 
tests  without  previously  being  split  off  by  decomposition. 
This  ferratin  and  hemoglobin  are  the  only  two  compounds 
in  the  body  containing  iron  combined  in  an  organic 
compound. 


(UtOA 


5>%    3tc^. 


^ 


^rlkjiMiM   ^  S^xha  QMum^jjM^ 


48  PHYSIOLOGICAL    CHEMISTRY. 

BLOOD. 

What  are  the  chief  chemical  constituents  of  blood? 


I. 

Proteids. 

"Serum  albumin.                          "^ 
Serum  globulin.                            — 

Fibrinogen   ( globulin  ) . 

Nucleo-proteid. 

Hemoglobin.                                   , 
Fats,  soaps  and  free  fatty  acids.      JL 

2. 

3- 

Carho  hydrates.                                    ^ 
Dextrose. 

4. 

Inorganic  salts. 

Alkali  phosphates,  chlorides,  sulphates,  and  car- 

bonates, of  Ca,  Mg,  Na,  K  and  Fe. 

What  is  the  specific  gravity  and  reaction  of  blood? 

Is  the  coloring  matter  in  the  plasma  or  corpuscles? 
Prove  by  experiment.  Which  are  larger,  the  cor- 
puscles of  warm-  or  cold-blooded  animals?  Cite  an 
experiment  to  illustrate  this. 

Specific  gravity  averages  1058  (highest  specific  gravity 
of  any  body  fluid). 

Reaction,  alkaline,  due  to  alkaline  phosphates  and 
carbonates. 

The  coloring  matter  is  in  the  red  corpuscles.  If  frog's 
blood  be  filtered,  the  red  coloring  matter  (corpuscles) 
will  be  left  on  the  filter  paper  and  the  filtrate  will  be 
almost  colorless. 

The  corpuscles  of  cold-blooded  animals  are  the  larger. 

When  human  blood  is  filtered,  the  corpuscles  pass 
through,  proving  they  are  smaller  than  the  pores  of  the 
filter  paper.    Frog's  corpuscles  will  not  go  through. 

What  are  prothrombin,  thrombin,  fibrinogen  and 
fibrin? 

Prothrombin  is  the  hypothetical  mother  substance  of 
thrombin,  or  fibrin  ferment.  Thrombin  is  synonymous 
with  fibrin  ferment  and  is  a  nucleo-proteid,  the  result  of 
the  influence  of  soluble  Ca  salts  upon  prothrombin. 
Fibrinogen  is  a  globulin  and  has  its  origin  in  the  destruc- 


50  PHYSIOLOGICAL    CHEMISTRY. 

tion  of  leucocytes.  Fibrin  is  a  coagulated  proteid  result- 
ing from  the  action  of  fibrin  ferment  upon  fibrinogen  in 
the  spontaneous  coagulation  of  blood. 

By  what  tests  would  you  detect  the  presence  of  blood 
in  a  stain? 

1.  Dissolve  a  portion  of  the  stain  in  a  few  drops  of 
glycerin  and  in  a  few  moments  examine  under  the  micro- 
scope.   The  corpuscles,  if  present,  will  be  shrunken. 

2.  Dissolve  the  rest  of  the  stain  in  water,  making  a 
concentrated  extract.  Place  some  before  the  spectroscope 
and  observe  if  the  two  specific  absorption  bands,  charac- 
teristic of  hemoglobin,  are  present. 

3.  Guaiacum  Test  (for  hemoglobin).  To  a  very  weak 
solution  of  the  suspected  blood,  add  a  few  drops  of  guaia- 
cum tincture  and,  then,  a  few  drops  of  old  turpentine 
(containing  ozone).  A  bluish  ring  results  at  the  zone  of 
contact  if  hemoglobin  is  present.  This  test  does  not  con- 
clusively prove  the  presence  of  hemoglobin,  as  pus  and 
other  substances  will  give  the  reaction. 

4.  Hemin  Test. — An  absolute  test  for  blood.  To  a  drop 
of  suspected  solution  on  a  slide  glass,  add  a  minute  grain 
of  NaCl.  Dry  carefully  over  the  flame ;  when  perfectly 
dry,  add  a  drop  of  glacial  acetic  acid ;  cover  with  cover 
glass  and  gently  warm.  When  cool,  examine  under  mi- 
croscope for  hemin  crystals. 

The  acetic  acid  splits  up  the  hemoglobin  into  globin 
and  hematin.  The  NaCl  reacts  with  the  acetic  acid  form- 
ing Na  acetate  and  nascent  HCl.  The  HCl  unites  with 
the  hematin  forming  hematin  hydrochloride  =  hemin 
(chocolate  color  crystals),  thus: 

Hemoglobin  CH3COOH  NaCl 

/  \  /  \ /     \ 

Globin         Hematin         CH3COO     ;  H  cl  |         Na 


How  may  the  coagulation  of  blood  be  (i)   retarded, 
(2)  accelerated? 

Retarded  by  Accelerated  by 

1.  Cold.  I.  Warming  slightly. 

2.  Addition  of  K  oxalate.  2.  Contact  with  foreign  bodies. 


k 


52  PHYSIOLOGICAL    CHEMISTRY. 

3.  Addition  of  strong  salts.  3.  Small  amount  of  water. 

4.  Addition  of  much  H2O.  4.  Admission  of  air. 

5.  Superabundance  of  CO2  (as-      5.  Diseases  of  the  intima. 

phyxia). 

6.  Injection  of  peptone, 

7.  Electric  current. 

Describe  the  method  for  detecting  the  blood  of  a  cer- 
tain animal. 

Precipitin  Test. — Blood  of  one  animal  is  repeatedly 
injected,  in  small  amounts,  into  the  system  of  an  animal 
of  a  different  species.  If,  after  several  inoculations, 
some  of  the  blood  or  serum  of  this  "  adapted  "  animal  is 
mixed  with  the  blood  or  serum  of  an  animal  of  the  first 
species,  a  precipitate  will  form. 


FOODS. 

What  is  the  relative  food  value  of  carbohydrates,  fats, 
and  proteids? 

The  value  of  a  food  depends  upon:  i.  The  amount  of 
energy  it  will  yield  the  body.    2.  Its  ability  to  form  tissue. 

Fats  and  carbohydrates  are  heat  producers,  the  former 
represents  the  body's  store-house  of  energy,  and  carbo- 
hydrates, its  immediate  supply. 

Proteids  figure  mainly  in  tissue  production.  All  struc- 
tural materials  contain  N  and  hence  in  the  repair  and 
building  of  structural  elements,  proteid  food  is  absolutely 
essential.    Without  some,  the  animal  cannot  exist. 

MILK.    !^^<ltJ^aJLMMxuir 

What  are  the  chief  constituents  of  milk? 

1.  Proteids — •  , 

Caseinogen.     ^'  ^  '^' 

Lact-albumin. 

Lact-globulin. 

2.  Fats — 

Ordinary  fats. 

Fats    of    the    lower    fatty    acids,    especially    tri- 
butyrin  and  tri-caproin. 


OkilmjuujfiM 


/VH^OH    ^.  litdt,   t^.  (|£<4uiiAttA/, 


54  PHYSIOLOGICAL    CHEMISTRY. 

3.  Carbohydrates—  ^    fCtu ^^^  ^M  ^^mji^uaji.  • 

Lactose.  ^"^  '         "^^ 

Slight  amount  of  dextrose. 

4.  Inorganic  materials — 

Phosphates  of  calcium. 
Citrate  of  calcium  (traces). 
Chlorides  of  potassium  and  sodium. 

5.  Extractives  (few). 

6.  Water. 

Describe  milk. 

Milk  is  an  emulsion  consisting  of  finely  divided  fat 
suspended  in  a  solution  of  proteid  bodies,  milk-sugar  and 
salts.  Specific  gravity  is  1030.  In  contains  scarcely  any 
extractives  and  is  an  excellent  food.  Its  reaction,  when 
fresh,  is  amphoteric  or  faintly  alkaline,  due  to  basic  phos- 
phates. It  gradually  changes  when  exposed  to  the  air 
and  its  reaction  becomes  more  and  more  acid,  due  to  a 
gradual  transformation  of  the  milk-sugar  into  lactic  acid, 
caused  by  micro-organisms. 

Write  the  reaction  involved  in  the  conversion  of  milk- 
sugar  into  lactic  acid.  How  could  you  prove  the 
presence  of  free  lactic  acid? 

The  milk-sugar  is  first  hydrated  and  then  transformed 
into  lactic  acid,  thus : 

C12H22OU  -f  H2O  =  2C«Hi20, 

CeHisOc  =  2C3Ha03. 

Lachmoid  paper  is  turned  red,  proving  the  presence  of 
free  acid. 

Explain  the  spontaneous   "  curdling "  of  milk. 

Caseinogen,  the  typical  proteid,  exists  in  milk  in  the 
form  of  a  salt,  which  salt  is  soluble  in  alkaline  or  neutral 
solutions.  As  the  milk  becomes  more  and  more  acid, 
''  sour,"  upon  exposure  to  the  air,  this  salt  is  acted  upon, 
and  casein  is  precipitated.  In  so  doing,  the  casein  en- 
tangles fat  globules  and  large  quantities  of  calcium  phos- 
phate. This  mass  constitutes  the  curd.  The  same  result 
may  be  obtained  by  adding  acid  to  fresh  milk.     An  im- 


^^W(i>^3 


M-  Uxu  -Ihaa  QMdi 


iji^OAk^.     \U"t 


y 


56  PHYSIOLOGICAL    CHEMISTRY. 

mediate  precipitate  of  casein  will  follow.     The  filtrate  is 
the  whey. 

A.  Name  the  leading  constituents  of  (a)  wheat  flour, 
(6)  potato,  (c)  bread. 

B.  How  may  the  most  important  in  each  be  identified? 

(a)   Wheat  flour |  l^^^'^J'  (proteid). 

{h)   Potato- 
Starch. 

Proteid. 

Fat. 

K2HPO4. 
(c)   Bread — 

Starch. 

Dextrin. 

Proteid. 

Fats. 
Starch  is  most  conspicuous  in  each.     It  may  be  identi- 
fied by  the  I  test. 

What  changes  does  flour  undergo  in  its  conversion 
into  bread? 

1.  The  starch  granules  are  disrupted,  the  cellulose  cap- 
sules being  broken. 

2.  Porosity  is  produced. 

3.  The  gluten  is  much  swollen. 

4.  Some  starch  in  the  crust  is  transformed  into  dextrin. 

What  is  the  leading  constituent  of  lemon?    How  may 
*  it   be   extracted?      Do   organic   acids   increase   the 

t  acidity  of  the  urine? 

Citric  Acid. — To  filtered  lemon  juice  add  CaCOg  till 
neutral  and  warm  on  water  bath.  Calcium  citrate  and 
CO2  are  formed.  Add  a  small  amount  of  water  and 
5  c.c.  diluted  H2SO4.  CaS04  precipitates  out  and  citric 
acid  remains  in  solution.  Filter.  Evaporate  the  filtrate  to 
small  bulk  and  citric  acid  will  crystallize  out  on  cooling. 

No.  Citric  acid  and  similar  organic  acids  are  converted 
into  carbonates  and  bicarbonates  and  increase  the  alka- 
linity of  the  urine. 


58  PHYSIOLOGICAL    CHEMISTRY. 

DIGESTION. 

What  is  digestion? 

Digestion  is  a  process  by  which  food  materials  are  trans- 
formed into  substances  capable  of  being  utiHzed  by  the 
body.  The  nutritious  elements  are  separated  from  the 
useless,  the  latter  being  excreted. 

What  are  the  various  kinds  of  digestion? 

Salivary,   gastric,   pancreatic,   intestinal   and   bacterial. 

What  are  zymogens,  enzymes,  anti-enzymes  and  anti- 
toxins?   Also  their  chemical  function. 

Zymogens  occur  in  the  cells  as  the  predecessors  of  en- 
zymes and  are  transformed  by  special  influence  into  en- 
zymes.   Thus,  pepsinogen  is  the  zymogen  of  pepsin. 

Enzymes  are  unorganized  ferments,  products  of  the 
chemical  processes  in  cells.  No  enzyme  has  ever  been 
separated  and  analyzed  in  a  pure  state  and  hence  their 
elementary  composition  is  unknown.  They  are  catalytic 
agents,  their  action  depending  upon — 

1.  Reaction   of  the   solution. 

2.  Temperature. 

3.  Presence  of  H2O. 

4.  Removal  of  the  products  of  the  reaction. 
Anti-enzymes  are  the  antagonists  of  enzymes,  having 

a  neutralizing  effect  upon  enzymes.  Thus,  a  stomach  ex- 
tract will  destroy  the  action  of  enzymes  of  the  stomach. 
If  it  were  not  for  these  anti-enzymes,  the  stomach  would 
probably  digest  itself. 

Anti-toxins  are  unorganized  ferments  existing  in  the 
wall  of  the  lower  part  of  the  alimentary  canal  and  are 
antagonistic  to  all  toxic  elements  entering  the  canal. 


ed(t&|iua0 


biJr&jjiOt 


^\Lxyi.(i..'X 


6o  PHYSIOLOGICAL    CHEMISTRY. 

SALIVARY  DIGESTION. 

What  is  salivary  digestion? 

Salivary  digestion  is  essentially  a  digestion  of  carbo- 
hydrates. Polysaccharides  are  transformed  through  the 
action  of  ptyalin  into  disaccharides,  and  a  small  amount 
of  disaccharrde7~due  to  an  invertin,  into  monosaccharide. 
Proteids,  fats  and  inorganic  salts  are  not  affected. 

What  is  saliva?     What  are  its  constituents? 

Saliva  is  a  mixture  of  the  secretions  of  the  submaxil- 
lary, parotid,  sublingual,  and  buccal  glands. 

Physical  Characteristics. — It  is  a  colorless,  translucent 
liquid  and  when  poured  from  one  vessel  to  another  is 
glairy  and  somewhat  viscid. 

Chemical  Ingredients, — Its  reaction  is  alkaline  due  to 
alkaline  phosphates  and  carbonates.  The  total  solids  are 
.5  per  cent.  Of  these,  the  organic  constituents  are  mucin,^ 
coagulable  proteid,  epithelial  cells  and  bacteria.  The 
inorganic  materials  are  HoO,  salts  of  the  alkaline  and 
earthy  metals,  phosphates,  chlorides,  sulphates,  and  potas- 
sium sulfo-cyanide. 

Enzymes. — Chief  enzyme  is  ptyalin.  An  invertin  is  also 
present  in  small  amounts. 

How  would  you  test  for  the  presence  of  (a)   mucin, 
(h)  coagulable  proteid,  {c)  potassium  sulfo-cyanide? 

(a)  To  a  small  amount  of  saliva,  add  a  few  drops  of 
acetic  acid.    The  precipitate  is  mucin,  a  gluco-proteid. 

(&)   Heat.    A  slight  opalescence  results. 

{c)  Put  a  few  drops  of  saliva  in  a  porcelain  dish 
(crucible).  Add  a  drop  of  dilute  HCl  and  dilute  ferric 
chloride.  A  red  color  results.  The  amount  of  potassium 
sulfo-cyanide  is  increased  after  using  tobacco. 

Describe  the  enzyme  ptyalin. 

Ptyalin  is  an  amylolytic  enzyme  and  converts  starch 
into  dextrins  and  sugars.  It  acts  best  in  a  neutral  solu- 
tion, though  dilute  alkaline  solutions,  as  saliva,  do  not 
impair  its  action.     Mere  traces  of  acid  do. 


62 


PHYSIOLOGICAL   CHEMISTRY. 


What  is  the  effect  of  temperature  upon  the  action  of 
ptyalin? 

Cold  retards  its  action  and  much  heat  completely  de- 
stroys the  enzyme.  The  optimum  temperature  is  about 
40°  C.  This  is  the  general  case  with  enzymes — cold  re- 
tards but  heat  "  kills." 

Give  a  table  of  the  breaking  down  of  starch  in  salivary 
digestion. 


Starch 


Soluble  starch 

-I 

Erythrodextrin 

"f 

Achroodextrin 

111 


Maltodextrin 


—I 

Maltose  r;  •>  Maltose 

I        I 

(Invertin)  Glucose     Glucose 


H2O 
I 


Iodine.      Fehling's  Sol. 
Blue 


Blue 


Red 


GASTRIC  DIGESTION. 
What  is  gastric  digestion? 

Gastric  digestion  is  essentially  a  digestion  of  proteids. 
Fat  also  is  slightly  emulsified  due  to  the  digestion  of  pro- 
teid  capsules  inclosing  fat  globules.  The  food  is  con- 
verted into  a  pulpy  mass  called  chyme. 

What  is  the  composition  of  gastric  juice? 

Like  saliva,  it  is  about  99.5  per  cent,  water.  It  is  dis- 
tinctly acid,  due  to  HCl  of  a  strength  approximately  .2 
per  cent.  The  important  enzymes  are  pepsin  and  rennin. 
Lipase  and  an  invertin  are  present  in  smalFamounts. 


64  PHYSIOLOGICAL    CHEMISTRY. 

How  would  you  prepare  a  gastric  extract  and  at  the 
sanie  time  illustrate  peptic  digestion. 

Cover  the  mucous  membrane  of  a  pig's  stomach  with 
4  per  cent.  HCl.  The  mucous  membrane  contains  pep- 
sinogen, the  zymogen  of  pepsin.  When  acid  and  pepsino- 
gen come  into  contact,  pepsin  results.  This  converts  the 
proteids  of  the  membrane  into  soluble  materials  (diges- 
tion) without  affecting  the  strength  of  the  pepsin. 

Can  dilute  HCl  alone  digest  proteids?     Can  pepsin? 

No.  If  fibrin  is  put  in  a  .2  per  cent.  HCl  solution,  it 
merely  swells  up.  Pepsin,  alone,  has  absolutely  no  effect 
on  proteids,  but  must  act  in  an  acid  medium.  A  solution 
of  pepsin  and  HCl  is  called  ''  pepsin — HCl." 

Is  the  HCl  in  a  free  or  combined  state?     What  tests 
would  you  employ  to  prove  the  presence  of  free  HCl? 

In  health  the  HCl  is  partly  free  and  partly  combined 
with  proteids.  That  which  is  in  proteid  combination  is 
nevertheless  physiologically  active. 

Giinzberg's  and  the  Tropaeolin  OO  test  (for  description 
see  chapter  on  Common  Tests). 

What  functions  may  be  ascribed  to  the  HCl  of  gastric 
juice? 

1.  The  most  important  function  is  the  destruction  of 
micro-organisms  entering  with  food. 

2.  It  converts  pepsinogen  into  pepsin. 

3.  Assists  pepsin  in  converting  the  proteids. 

4.  Slightly  favors  the  conversion  of  starch  into  sugar. 

5.  Causes  collaginous  materials  to  swell  and  become 
gelatinized.  Collaginous  materials  unless  thus  trans- 
formed are  indigestible. 

6.  Converts  prosecretin  into  secretin. 

7.  Increases  the  flow  of  pancreatic  juice. 

What  substances  give  rise  to  HCl? 

The  most  plausible  theory  is  that  NaCl  is  disintegrated 
by  large  amounts  of  COo,  thus,  NaCl  -f-  CO2  +  H2O  = 
NaHCOg  +  HCL.  The  bi-carbonate  may  also  react  with 
the  salt,  thus,  NaHCOg  +  NaCl  =  Na^COg  +  HCl. 


66  PHYSIOLOGICAL    CHEMISTRY. 

In  substantiation  of  this  theory,  the  urine,  soon  after 
meals,  becomes  alkaUne,  as  would  be  expected  from  the 
alkaline  carbonates  being  thrown  back  into  the  blood. 

Describe  pepsin.     Give  a  table  showing  its  stages  of 
digestion. 

Pepsin  is  a  proteolytic  enzyme,  inactive  in  neutral  or 
alkaline  solutions,  but  in  acid  solutions,  preferably  HCl, 
it  is  very  energetic.  It  converts  proteids  into  a  number 
of  substances,  the  simplest  of  which  is  peptone,  thus : 

Proteid. 

I 
Acid-proteid   (albuminate). 

/  \ 

Proto-proteose.        Hetero-proteose   (primary  proteose). 

Deutero-proteose.        Deutero-proteose   (secondary  proteose).  " 

Peptone.  Peptone. 

How  can  you  separate  proteoses  from  peptones? 

Take  the  solid  composed  of  these  two  substances  and 
add  water.  Boil  on  the  water  bath,  adding  (NH4)2S04 
to  saturation.  A  gummy  precipitate  of  proteose  will  form 
on  top.  The  proteose  precipitate  will  cling  to  the  stir- 
ring rod  and  the  sides  of  the  vessel.  The  peptone  remains 
in  solution.  Pour  off  the  liquid,  clean  out  the  vessel  and 
dissolve  the  gum  in  boiling  water.  This  will  be  a  proteose 
solution. 

There  are  two  kinds  of  proteoses  in  general — primary 
and  secondary.  The  primary  are  precipitated  by  concen- 
trated HNO3,  acetic  acid  and  K  ferro  cyanide,  while  the 
secondary  are  not.  Both  are  precipitated  by  picric  acid 
and  K  mercuric  iodide  with  HCl. 

What  is  the  effect  of  acids  and  alkalies  on  gastric  di- 
gestion?   Also  of  heat  and  bile? 

A  small  amount  of  alkali  destroys  the  action  of  the 
gastric  enzymes.  Dilute  acids,  except  oxalic,  and  neutral 
salts  do  not  affect  them.  Bile  retards  their  action;  ex- 
cessive heat  (70°  C.)  kills  the  enzymes. 


^u>^"-H 


6  W  -h 
^0  H 


i-O 


ft  a  r 


68 


PHYSIOLOGICAL    CHEMISTRY. 


Write  a  table  illustrating  the  different  effect  of  acid 
and  alkali  upon  pepsin  and  its  antecedent,  pep- 
sinogen. 


1. 

8. 

3. 

4. 

5. 

Glycerin  Ext. 

Glycerin  Ext. 

Glycerin  Ext. 

Glycerin  Ext. 

Pepsin  Solution. 

Fibrin. 

0.2  /„  HCl 
Fibrin. 

csf^Na^COs 
Fibrin. 

Fibrin. 

Eq.  Vol., 
15^  Na.COa 
Fibrin. 

No  Digestion 

Digestion. 

No  Digestion. 

No  Digestion. 

No  Digestion. 

Eq.  Vol.  0.45^ 

Neutralize  + 

Neutralize + 

Neutralize  + 

HCl 

Eq.  Vol.  0.  4i  HCl 

Eq.  Vol.  o.4iHCl 

Eq.  Vol  o.4$HCl 

Digestion. 

Digestion. 

Slight  digestion? 

No  Digestion. 

Compare  3  and  5. 
The  glycerin  extract  contains  the  zymogen,  pepsinogen,  which  is  not 
destroyed  by  the  dilute  alkali,  whereas  the  pepsin  itself  is  destroyed. 

What  is  rennin?     Can  it  act  alone? 

Rennin  is  an  enzyme  which  has  a  pecuHar  action  on 
milk,  converting  caseinogen  into  casein,  thereby  pro- 
ducing the  "  curd." 

Yes.  It  coagulates  the  milk  and  prepares  it  for  the 
action  of  the  pepsin  (HCl). 

What  substances  are  to  be  tested  for  in  stomach  analy- 
sis?   How  would  you  identify  each? 

First,  test  the  reaction  of  the  contents.  Filter  and  test 
for  free  HCl.  Under  the  microscope,  note  the  kind  of 
bacteria,  fungi,  cells,  etc.  Divide  the  filtrate  into  two 
parts  and  neutralize  one  portion. 


Filtrate. 


Neutralized — Test  for— 

Unchanged— 

I,  Albuminate. 

I.  Pepsin. 

2.  Proteose. 

2.  Lactic  acid 

3.  Peptone. 

3.  (Bile). 

4.  Ptyalin. 

5.  Rennin. 

6.  Sugar — Reducing  agents. 

7.  Starch. 

-Test  for- 


6      ^i./vA.o.J  iiiJA^i^tfjOft 


K  N 


.?  iUjM«;u'     JuM«£cUt^ 


70  PHYSIOLOGICAL    CHEMISTRY. 

If,  on  neutralizing,  there  is  a  precipitate,  albuminate 
is  present. 

Saturate  a  portion  with  (NH4)2S04.  The  gummy 
precipitate  is  proteose.  Filter.  Test  filtrate  with  Biuret 
test.  A  pink  coloration  indicates  peptone.  Test  a  fresh 
portion  for  ptyalin  by  trying  to  digest  starch  with  some 
of  the  solution.  To  another  portion  add  some  milk.  If 
there  is  curdling  rennin  is  present.  Test  for  sugar  with 
Fehling's  solution,  starch  with  I  test. 

To  test  for  pepsin,  add  to  a  portion  of  the  unchanged 
filtrate  some  fibrin  in  a  0.2  per  cent  HCl  solution.  Di- 
gestion indicates  pepsin.  For  lactic  acid,  treat  the  re- 
mainder with  carbolo-chloride  of  iron  (Uffelmann's  test). 
If  lactic  acid  is  present,  the  color  disappears  from  the 
solution. 

PANCREATIC  DIGESTION. 
Describe  pancreatic  juice. 

Pancreatic  juice  is  a  liquid  containing  from  4-10  per 
cent,  solids.  Its  important  constituents  are  an  albumin, 
similar  to  myosin,  giving  rise  to  clotting,  small  amounts 
of  fats  and  soaps,  and  a  comparatively  large  amount  of 
Na^COo  (5  per  cent.)  to  which  is  due  the  alkalinity  of 
the  juice.  There  are  five  enzymes  (or  their  zymogens), 
three  of  which  are  important,  trypsin,  amylopsin,  and 
lipase  or  steapsin.  Invertins  and  rennin  are  present  in 
small  amounts.  The  juice  is  remarkable  for  the  power  it 
possesses  of  acting  on  all  three  foodstuffs,  starch,  fat, 
and  proteid. 

(a)  What  is  trypsin?     Describe  its  action,     {h)  How 
does  it  differ  from  pepsin? 

{a)  Trypsin  is  the  proteolytic  enzyme  of  pancreatic 
juice. 

It  digests  proteids  in  alkaline,  neutral  or  very  faintly 
acid  solutions. 

{h)  Peptic  digestion  is  essentially  an  acid  digestion, 
tryptic  alkaline. 

In  pancreatic  digestion,  the  proteid  dissolves  without 
previously  swelling  up  as  in  gastric  digestion. 


\  XxJv  AiAA,'-^ 


72  PHYSIOLOGICAL   CHEMISTRY. 

The  essential  difference  is  that  in  gastric  digestion,  the 
products  are  not  carried  beyond  the  proteid  stage;  in 
pancreatic  digestion,  much  of  the  proteid  is  transformed 
into  something  which  is  no  longer  proteid.  Therefore, 
tryptic  digestion  puts  on  the  finishing  touches  to  the  work 
begun  in  gastric  digestion,  thus : 

Gastric  Digestion.  Pancreatic  Digestion. 

Proteid.  Proteid. 

I  I 

Acid  Proteid.  Alkaline-Proteid. 

„  I  I 

Proteose.  Proteose. 

„  I  I 

Peptone.  Peptone. 

/       \    . 
Lysin.       Leucin. 

Arginin.    Tyrosin. 

Histidin.  Tryptophan,  etc. 

What  is   the   effect  of  various   chemicals  on  tryptic 
digestion? 

Free  acids  prevent  digestion.  Metallic  salts  retard, 
while  ordinary  neutral  salts,  in  small  amounts,  do  not 
affect  its  action.  Alcohol,  ether,  chloroform  and  bile, 
when  not  present  in  excess,  have  no  harmful  effect. 

What  is  lipase?    Describe  its  action. 

Lipase  is  the  fat-splitting  enzyme  of  pancreatic  juice. 

Its  action  is  two-fold.  First,  it  emulsifies  fat  and 
secondly,  has  the  property  of  splitting  neutral  fats  into 
glycerin  and  fatty  acid. 

What  is  amylopsin?    Describe  its  action. 

It  is  an  amylolytic  enzyme,  being  a  sort  of  concen- 
trated ptyalin.  Its  action  is  the  same  as  this  substance, 
carrying  on  the  work  of  digesting  carbohydrates  not 
already  completed  by  saliva. 

On  starch,  it  acts  with  great  rapidity,  converting  it  into 
sugar,  chiefly  maltose.  The  invertins  in  the  pancreatic 
juice  most  probably  convert  the  maltoses  into  dextrose. 


74  PHYSIOLOGICAL    CHEMISTRY. 

What  are  the  functions  of   (a)   secretin,   (b)   entero- 
kinase  (c)  erepsin? 

Secretin  is  formed  by  the  action  of  HCl  on  the  pre- 
formed prosecretin  in  the  intestinal  cells.  It  is  absorbed 
into  the  blood  and  upon  reaching  the  pancreas,  stimulates 
its  secretion. 

Enterokinase,  a  product  of  intestinal  secretion,  con- 
verts trypsinogen  into  trypsin. 

Erepsin  converts  peptones  into  nitrogenous  crystalline 
bo3t^54rsr^leucin,  tyrosin,  tryptophan,  etc.  Perhaps  tryp- 
sin does  not  transform  proteid  beyond  the  peptone  stage ; 
in  this  case,  erepsin  is  a  necessary  adjunct. 

What  are  leucin  and  tyrosin?     Write  their  constitu- 
tional formulae. 

Leucin  and  tyrosin  are  two  of  the  end  products  of  pan- 
creatic digestion.  They  are  nitrogenous  crystalline  bodies 
and,  under  the  microscope,  exhibit  characteristic  crys- 
tals; those  of  leucin  are  globular,  tyrosin  crystals  ap- 
pearing as  bundles  of  needles   (sheaves). 

Leucin  is  amino-iso-butyl-acetic  acid  or  amino  caproic 
acid. 

CHq  CHq 

\/ 

GH 

CH,  •  or  C.uy 

I  \COOH 

COOH 
Tyrosin  is  oxy-pheno!^amino-propionic  acid. 

/OH 
QH  /  NH, 

\qH3/ 

\COOH 

What  is  Hofmann's  test? 

Hofmann's  test  is  a  test  for  tyrosin  with  Millon's 
reagent.  A  beautiful  red  color  results  due  to  the  phenol 
radicle  in  tyrosin. 


o 
A  e  H 


"J^y  PHYSIOLOGICAL    CHEMISTRY. 

What  is  the  destiny  of  the  various  enzymes? 

Ptyalin  is  completely  lost  after  it  passes  into  the  py- 
loric end  of  the  stomach.  Pepsin  disappears  after  its 
entrance  into  the  duodenum.  The  pancreatic  enzymes 
cease  to  act  before  reaching  the  rectum.  The  only  en- 
zymes in  the  faeces  are  those  of  bacteria. 

Occasionally  enzymes  appear  in  the  blood  and  urine. 


BILE. 
Describe  bile. 

Bile  is  a  juice  secreted  by  the  hepatic  cells.  Its  secre- 
tion is  continuous,  the  fluid  being  stored  in  the  gall  blad- 
der until  required  in  the  intestines.  When  fresh,  it  is 
a  bright  golden  yellow,  changing  to  a  green  after  reten- 
tion in  the  gall  bladder.  From  the  bladder  it  acquires  a 
colloidal  material,  mucin,  giving  the  fluid  a  ''  thread  pull- 
ing," ropy  character. 

What  is  the  composition  of  bile? 

It  is  an  alkaline  fluid,  containing  about  15  per  cent, 
solids.  The  substances  giving  the  character  to  it,  are  the 
bile  salts  and  bile  pigments.  In  addition  it  contains  in- 
organic salts,  cholesterin,  lecithin  and  soaps. 

What  is  the  influence  of  bile  upon  digestion? 

Bile  contains  no  enzymes  and  hence  is  not  strictly  a 
digestive  juice.  But  due  to  its  salts,  it  favors  digestion 
by  having  a  two-fold  action  on  fats.  First,  it  emulsifies 
them,  paving  the  way  for  the  action  of  lipase  in  splitting 
fats  into  glycerin  and  free  fatty  acids.  The  Na  of  the 
bile  salts  then  unites  with  the  free  fatty  acids,  forming 
soaps,  which  soaps  in  turn  aid  the  further  emulsion  of 
fats ;  secondly,  bile  favors  the  absorption  of  fats.  Hence, 
it  is  an  important  adjunct  to  pancreatic  juice  in  aiding 
both  the  emulsification  and  absorption  of  fat. 

What  are  the  functions  of  bile? 

The  functions  of  bile  are : 

1.  To  dissolve  and  emulsify  fats. 

2.  To  hold  soaps  in  solution. 


78  PHYSIOLOGICAL    CHEMISTRY. 

3.  To  aid  in  the  alkalinity  of  the  intestines  and 
thereby  prepare  the  way  for  the  action  of  pancreatic 
juice. 

4.  To  hold  cholesterin  in  solution. 

5.  To  serve  as  an  excretory  medium  for  cholesterin, 
pigments  and  metallic  substances. 

/5.  To  stimulate  the  flow  of  trypsin. 

7.  To  stimulate  the  flow  of  bile. 

8.  To  stimulate  the  flow  of  intestinal  fluids. 
\^.  To  promote  peristalsis. 

10.  To  act  as  a  preventative  agent  of  putrefaction. 

11.  To  precipitate  proteoses.  "v 

12.  To  favor  the  action  of  amylopsin. 

What  are  the  bile  salts?    Write  the  constitutional  for- 
mulae of  glycocoU  and  taurin. 

The  two  bile  salts  are  Na  glycocholate  and  Na  tauro- 
cholate.  They  consist  of  Na  and  the  conjugate  cholic 
acid  united  with  glycocoU  and  with  taurin. 

GlycocoU  is  amino-acetic  acid. 

\COOH 


Taurin  is  amino-ethyl-sulphonic  acid, 
so/ 

\0H 
What  is  the  test  for  bile  salts? 

Pettenkofer's  Test. — To  some  bile  in  a  porcelain  dish, 
add  a  grain  of  sugar.  Then  drop  in,  from  a  pipette, 
concentrated  H2SO4.    A  brilliant  cherry-red  color  results. 

The  H2SO4  disintegrates  the  bile  salts  and  attacks 
the  sugar,  making  furfurol.  This  furfurol  and  the  cholic 
acid  react  to  produce  the  red  coloration. 

What  is  (a)  the  function  of  these  bile  salts?  (b)  their 
destiny? 

The  various  functions  above  attributed  to  bile  are  due 
to  these  salts. 


S-^j 


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5-   I 

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8o  PHYSIOLOGICAL    CHEMISTRY. 

Most  of  the  bile  salts  are  absorbed  by  the  intestines 
(bile  is  a  good  cholagogue).  The  remainder  is  decom- 
posed by  the  HCl  from  the  stomach  as  follows : 

Bile  salts  (Na)  +  HCl. 

/  I  \ 

Glycocoll     NaCl  Cholic  acid 

Taurin 

Practically  all  the  glycocoll  and  taurin  is  absorbed  to 
form  more  bile  salts.  The  rest  of  the  glycocoll  and 
taurin  appears  in  the  urine  respectively  as  hippuric  acid 
and  indican. 

The  cholic  acid  is  dehydrated  through  choloidinic  acid 
to  dyslysin  thus : 

Cholic  acid  C24H40O5  —  H2O  = 
Choloidinic  acid  C24H38O4  —  HgO  = 
Dyslysin  C24H36O3 

This  dyslysin  is  excreted  in  the  faeces. 

What  are  the  bile  pigments? 

The  two  normal  pigments  are  bilirubin  (red)  and  bili- 
verdin  (green).  BiHcyanin  (blue),  bilipurpurin  (pur- 
ple), and  bilixanthin  (reddish  yellow),  are  oxidation 
products  of  the  two  normal  pigments. 

What  is  the  test  for  bile  pigments  ? 

Gmelin's  Test. — To  a  small  amount  of  bile,  in  an 
evaporating  dish,  add  from  time  to  time,  with  the  aid  of 
a  pipette,  a  few  drops  of  nitric  acid  containing  nitrous 
acid.  There  will  be  a  series  of  colors  beginning  with  green 
and  passing  through  blue,  violet  and  red  to  reddish- 
yellow.  These  successive  colors  result  from  the  oxida- 
tion of  the  pigments,  due  to  the  nitrous  acid. 

What  is  the  origin  of  the  pigments? 
What  reason  would  you   give   to   confirm   this   con- 
clusion ? 

The  pigments  result  from  the  destruction  of  the  hemo- 
globin of  the  blood.  The  relation  of  bilirubin  to  hemo- 
globin is  as  follows : 


(h^^JiUbi 


last-    ~     d^^     p /QL-<4jUsL=:*^' 


82  PHYSIOLOGICAL    CHEMISTRY. 

Hemoglobin. 

/  \ 

"  Globin."  Hematin, 

C32H3oN404Fe 
—  Fe  +  2H2O 

2   I    a2H36N406 

C16H1SN2O3  =  bilirubin. 

Thus  by  the  addition  of  two  molecules  of  water  the 
hemoglobin  is  transformed,  after  throwing  off  its  iron 
component,  into  bilirubin. 

This  view  is  supported  by  the  fact  that 

1.  The  hepatic  cells  contain  a  peculiar  iron  content 
(ferratin). 

2.  Animals  containing  no  hemoglobin  in  their  blood, 
secrete  no  bile  pigments. 

3.  If  hemoglobin  be  injected  into  the  blood,  there  will 
be  an  increase  in  bile  pigments. 

4.  Hematoidin  (found  in  black  eyes,  old  blood  clots, 
etc.),  and  bilirubin  have  the  same  formula. 


ABSORPTION,   BACTERIAL   DIGESTION   AND 
FAECES. 

What  changes,  if  any,  do  water  and  salts  undergo  in 
digestion? 

Water  is  merely  warmed  before  being  absorbed  by 
the  intestines.  From  them,  it  passes  directly  into  the 
blood. 

Saline  substances  are  not  much  affected.  They  may 
be  converted  from  acid  into  alkali  or  vice  versa,  depend- 
ing upon  the  action  of  the  digestive  medium.  They  are 
usually  absorbed  in  molecular  form. 

(Organic  acids  all  undergo  essentially  the  same  decom- 
position and  are  absorbed  as  salts,  usually  of  Na.  They 
are  utilized  in  combustion,  carbonates  resulting,  thus  help- 
ing to  maintain  the  normal  alkalinity  of  the  blood.) 


-  9-ja-  -1-1/4  t,o 


84  PHYSIOLOGICAL    CHEMISTRY. 

Indicate  the  nature  and  extent  of  the  chemical  changes 
which  carbohydrates  undergo  until  they  or  their 
products  are  absorbed  and  transformed  in  the  liver 
into  glycogen. 

In  salivary  digestion,  starch  is  acted  upon.  This  ac- 
tion continues  for  some  time  in  the  cardia  of  the  stomach, 
maltose  being  the  final  product.  The  little  invertin  in 
saliva  may  convert  a  trifle  into  glucose.  Some  of  the 
starch  thus  passes  into  the  intestine  as  maltose,  but 
much  has  to  be  transformed  by  amylopsin,  yielding  malt- 
ose as  the  final  product.  The  pancreatic  invertins^  con- 
vert the  maltose  into  glucose.  Disaccharides  are^ot  af- 
fected until  they  reach  the  small  intestine,  where  the 
pancreatic  invertins  transform  them  into  monosaccharides 
as  follows : 

Lactose  Sucrose  Maltose 

/  \  /  \  /  \ 

Glucose     Galactose  Glucose     Levulose  Glucose     Glucose 

Carbohydrates  are  absorbed  as  monosaccharides  and 
appear  as  such  in  the  blood.  Reaching  the  liver  by  the 
portal  vein,  the  glucose,  by  dehydration  and  polymeriza- 
tion, is  converted  into  glycogen,  which  substance  is  the 
ultimate  product  of  carbohydrate  digestion. 

Carbohydrates  normally  undergo  certain  fermentations 
in  the  stomach,  yielding  CO2,  alcohol,  acetic,  tartaric, 
and  butyric  acids  in  minute  quantities.  In  indigestion, 
there  is  a  superabundance  of  these.  Fermentative  proc- 
esses increase  after  leaving  the  stomach,  but  are  less 
harmful  in  the  intestines.  In  the  large  intestine  of  herbiv- 
orous animals,  there  is  extensive  fermentation  to  con- 
vert cellulose  into  soluble  materials. 

State  the  changes  which  fats  undergo  from  their  en- 
trance into  the  body  until  their  appearance  in  the 
lacteals. 

In  the  mouth,  fats  are  melted  and  in  the  stomach,  the 
peristaltic  action  makes  a  crude  emulsion  of  them.  A 
very  slight  change  to  glycerin  and  fatty  acid  may  occur 
due  to  traces  of  lipase. 


86  PHYSIOLOGICAL    CHEMISTRY. 

In  the  intestines,  upon  meeting  the  alkaline  pancreatic 
juice,  bile,  etc.,  further  emulsion  takes  place.  Due  to  the 
action  of  lipase,  the  fats  are  dissociated  into  glycerin  and 
free  fatty  acids.  Some  free  fatty  acid  unites  with  the 
alkalies,  forming  soaps,  chiefly  Na.  Due  to  the  bile, 
soaps,  glycerin  and  fatty  acids  are  kept  in  solution. 

It  is  believed  that  fat  is  absorbed  in  these  forms, 
namely,  glycerin,  fatty  acid,  and  soap  and  synthesized 
again,  in  the  columnar  cells,  into  neutral  fats.  From 
these  cells  it  passes,  as  minute  droplets,  through  the 
reticular  tissue  of  the  villi,  to  the  lacteals. 

Trace,   step  by  step,   the   changes  that  proteid  food 
undergoes  in  its  conversion  into  serum  albumin. 

The  first  changes  occur  in  the  stomach,  due  to  pepsin. 
Some  of  the  proteid  is  converted  through  the  stage  of 
acid  albuminate  into  primary  and  secondary  proteose  and 
into  peptone.  Some  of  the  proteose  and  peptone  is  ab- 
sorbed in  the  stomach,  appearing  in  the  blood  as  serum 
albumin.  The  remaining  proteid  material  ejected  from 
the  pylorus  is  acted  upon  by  trypsinogen  and  is  converted 
into  proteose  and  peptone.  Most  of  the  proteose  and 
peptone  is  absorbed  as  such,  appearing  in  the  blood,  not 
as  proteose  and  peptone,  but  serum  proteid.  But  tryp- 
sinogen, in  conjunction  with  erepsin,  converts  some  of  the 
proteose  and  peptone  into  products  that  are  no  longer 
proteid,  namely,  into  nitrogenous  crystalline  bodies  as 
leucin,  tyrosin,  tryptophan,  etc.  These  crystalline  products 
rapidly  disappear  from  the  intestinal  fluid  but  cannot  be 
detected  in  the  intestinal  wall  or  blood-vessels.  Instead, 
there  is,  in  the  blood,  an  increase  of  serum  albumin.  Evi- 
dently these  substances  are  immediately  reconstructed 
in  the  intestinal  epithelium  into  serum  albumin. 

Just  as  carbohydrates  undergo  bacterial  changes,  called 
fermentation,  so  proteids  undergo  similar  changes  termed 
putrefaction.  The  characteristic  products  of  intestinal 
putrefaction  are : 

Reducing  Gases. — CO2,  HoS,  CH4,  NH3. 

Aromatic  Bodies. — Indol,  skatol,  phenol  and  para- 
kresol. 


PHYSIOLOGICAL    CHEMISTRY. 


Write  the  formulae  for  indol,  skatol,  phenol  and  para- 
kresol.    What  becomes  of  the  indol  and  skatol? 

CH  C(CHo) 

CJL      CH  QH,       CH 


NH  NH 

Indol.  Skatol  or  methyl-indol. 

H  CH, 


OH  OH 

Phenol.  Parakresol  or  methyl-phenol. 

Some  of  the  indol  and  skatol  is  excreted  in  the  faeces, 
giving  to  them  their  characteristic  odor.  The  rest  of  the 
indol  is  absorbed  and,  reaching  the  liver,  is  hydrated  to 
indoxyl.  This  indoxyl  unites  with  a  sulphuric  acid 
radical,  forming  indoxyl-sulphuric  acid.  This,  in  turn, 
associates  itself  with  an  alkali,  forming  an  indoxyl  salt. 
This  salt  passes  into  the  urine  and  is  called  indican. 
Skatol  has  a  similar  destiny. 

Write  formulae  to  show  the  formation  of  indican  from 
indol. 

CH  C-OH 

/^  /       ^ 

I. 


C,H,     CH 

2.     CgH,           CH 

\/ 

\  / 

NH 

NH 

Indol. 

Indoxyl. 

CO-SO,H 

co-rsOgK) 

/       ^ 

/X 

CeH,           CH 

4.       CfiH,     CH 

\       / 

\/ 

NH 

NH 

[ndoxyl  H2SO4. 

Indican. 

(a)  Name  the   chief  constituents   present  in  normal 
faeces. 

(b)  Explain  the  occurrence  in  the  faeces  of  five  of 
these. 

In  the  faeces  are  found : 

I.  Digestible  constituents  of  food — muscle  fibres,  con- 
nective tissue  fibres,  starch  grains  and  fat. 


90  PHYSIOLOGICAL    CHEMISTRY. 

2.  Indigestible   bodies   as   keratin. 

3.  Constituents  of  different  secretions — dyslysin,  mu- 
cin, cholesterin  (stercolin). 

4.  Products  of  putrefaction  or  digestion — indol,  ska- 
tol,  phenol,  parakresol,  HgS,  NH4  and  mineral  bodies  as 
MgNH^PO^  and  calcium  and  magnesium  soap. 

5.  Alicro-organisms  of  various  species. 

(b)  I.  All  the  digestible  constituents  have  not  had 
sufficient  time  to  be  completely  digested  in  the  intestinal 
tract. 

2.  The  indigestible  substances  have  not  been  affected 
by  the  various  juices  and  hence  not  prepared  for  ab- 
sorption. 

3.  The  presence  of  the  secretory  constituents  shows 
that  the  faeces  is  an  important  channel  for  the  exit  of 
extraneous  secretions. 

4.  The  products  of  putrefaction  result  from  the  action 
of  bacteria  on  proteids. 

5.  The  micro-organisms  are  taken  in  with  the  food. 
Most  are  killed  in  the  stomach  by  the  HCl  but  some  pass 
through  the  pylorus,  mostly  as  spores.  These  germinate 
and  the  bacteria  continue  to  flourish  in  the  remainder  of 
the  intestinal  tract. 

URINE. 

Why  is  the  chemical  study  of  urine  important? 

Because  of  the  light  it  throws  on  the  metabolic  pro- 
cesses of  the  body  in  health  and  disease.  The  constitu- 
ents represent  end  products  formed  all  over  the  body 
(note  the  entire  absence  of  the  three  kinds  of  food- 
stuffs). 

What  are  the  chief  constituents  of  urine? 

The  (average)  daily  quantity  of  solids  is  60  grams. 

Organic  Bodies. — By  far  the  most  important  is  urea, 
constituting  one-half  of  the  total  solids.  Closely  allied 
to  urea,  is  uric  acid,  occurring  in  small  quantity. 

Creatinin,  hippuric  acid,  indican  and  the  purin  bases, 
(xanthin  and  hypoxanthin)  are  present  in  small  and 
variable  amounts. 


y 
^ 


92  PHYSIOLOGICAL    CHEMISTRY. 

Inorganic  Constituents. — The  chief  bases  are  Na,  K, 
Ca,  and  Mg  in  the  form  of  chlorides,  phosphates,  sul- 
phates and  oxalates.  NaCl  is  the  most  abundant  and 
important,  constituting  25   per  cent,  of  the  total  solids. 

What    is    the    quantity    of   urine    used    for   analysis? 
Why  this  quantity? 

The  quantity  taken  is  what  is  called  a  "  24  hour " 
urine,  meaning  the  amount  excreted  in  that  many  consec- 
utive hours.  This  quantity  is  used  because  the  composi- 
tion differs  when  voided  at  different  periods. 

What  is  the  reaction  of  urine?     What  conditions  in- 
fluence this? 

The  reaction  of  "24.  hour  "  urine,  under  normal  con- 
ditions, is  slightly  acid,  due  not  to  free  acids,  but  to  acid 
salts  as  NaH2P04. 

1.  The  reaction  depends  essentially  upon  the  compo- 
sition of  the  food.  Animal  food  yields  an  abundance  of 
acid  radicals,  while  vegetable  food  contains  organic  acids, 
readily  converted  into  basic  bodies. 

2.  The  amount  of  acid  radicals  withdrawn  from  the 
blood  for  specific  purposes  as  gastric  digestion. 

What  is  meant  by  the  alkaline  tide  of  the  urine? 

After  taking  food,  when  a  large  amount  of  gastric 
juice  containing  HCl  is  being  secreted,  the  alkalinity  of 
the  blood  is  temporarily  increased.  Synchronous  with 
this,  there  is  a  corresponding  increased  alkalinity  of  the 
urine,  which  is  called  the  ''  alkaline  tide."  The  urine 
becomes  turbid  due  to  the  precipitation  of  basic  Ca  and 
Mg  phosphates. 

Why  is  the  specific  gravity  of  urine  important?     As 
what  are  the  solids  determined? 

The  specific  gravity  is  an  indication  of  the  amount  of 
solids.  This  amount  cannot  be  reckoned  by  ordinary 
methods  of  analysis  due  to  the  fact  that  urea  decomposes 
liberating  NH3. 

The  determination  of  constituents  is  in  grams  per  24 
hours  and  not  percentage,  as  the  amount  of  liquid  is 
very  variable. 


94  PHYSIOLOGICAL    CHEMISTRY. 

What  is  the  specific  gravity  of  urine? 
How  is  the  amount  of  total  solids  determined  from 
this? 

The  average  specific  gravity  is  1020.  It  may  vary 
considerably. 

The  total  solids  are  determined  by  Christison's  formula. 
Multiply  the  last  two  figures  of  the  specific  gravity  by  the 
figure  2.34.    This  gives  the  grams  per  litre  of  solids. 

What  are  the  phosphates  in  the  urine? 
What  salts  are  precipitated  when  the  urine  is  made 
alkaline  ? 

There  are  four  phosphates. 

1.  The  alkaline  phosphates  of  Na  and  K  which  occur 
in  largest  amounts. 

2.  Soluble  earthy  phosphates  of  Ca  and  Mg. 

3.  Triple  phosphate  (magnesium  ammonium  phos- 
phate) which  crystallizes  in  regular  forms  in  the  shape 
of  coffin-lids  and  which  proves  that  urea  has  decomposed. 

4.  Stellar  phosphate.  The  latter  two  are  abnormal 
constituents. 

The  earthy  phosphates  are  completely  precipitated  in 
alkaline  urine. 

What  is  urea? 

Urea  is  the  most  important  nitrogenous  end  product 
of  proteid  metabolism.  About  nine-tenths  of  the  ■  N  in 
proteid  food  passes  off  in  this  form.  Though  a  base, 
forming  salts  with  such  acids  as  nitric  and  acetic,  it  occurs 
in  the  urine  in  an  absolutely  free  condition. 

How  is  urea  formed  in  the  body? 

Practically  all  the  N  of  proteids  is  converted  into  amino 
acids  before  regeneration  occurs.  In  digestion,  these 
amino  acids  are  taken  into  the  villi  and,  appearing  in  the 
blood  as  serum  proteid,  are  reconverted  into  tissue  pro- 
teids. Later,  these  are  broken  down  into  amino-acids, 
creatinin,  etc.,  and  finally  into  NH3,  CO2,  and  HgO. 
The  NH3  is  poisonous  and  immediately  combines  with 


96  PHYSIOLOGICAL    CHEMISTRY. 

the  CO2  and  HgO  forming  (NH4)2C03.  This  ammonium 
carbonate  is  dehydrated  into  less  poisonous  ammonium 
carbamate.  This  in  turn,  by  the  expulsion  of  a  molecule 
of  water,  yields  urea,  thus : 


/ONH, 
\ONH4 

-H^O      = 

/ONH, 
\NH2 

Am.  Carbonate. 

Am.  Carbamate, 

/ONH^ 
0  =  C  < 

\NH2 

-H2O      = 

Am.  Carbamate. 

Urea. 

This  transformation  takes  place  in  the  liver. 
How  may  urea  be  prepared? 

To  a  litre  of  urine,  add  150  c.c.  of  baryta  mixture 
(one  part  barium  nitrate  to  two  parts  barium  hydroxide). 
This  precipitates  the  phosphates  and  sulphates.  Filter. 
The  filtrate  contains  all  but  the  inorganic  substances. 
Pour  in  a  small  beaker  of  alcohol.  Stir  thoroughly  and 
filter.  The  filtrate  contains  the  urea,  creatinin  and  pig- 
ments. Evaporate  on  a  water-bath  to  small  bulk.  Upon 
cooling,  crystals  of  urea  will  separate  out. 

What  is  a  good  qualitative  test  for  urea? 

From  concentrated  solutions,  urea  combines  with  such 
acids  as  nitric  and  oxalic,  forming  crystals  of  charac- 
teristic shape.    The  test  with  nitric  is  the  best. 

How  may  the  amount  of  urea  in  urine  be  estimated? 

It  may  be  determined  in  terms  of  the  N  which  it 
liberates. 

Hypohromite  Method. — This  test  depends  upon  the 
fact  that  urea  is  decomposed  by  an  alkaline  solution  of 
sodium  hypobromite,  yielding  N,  HgO,  and  COg,  thus : 

CO  <  -1-  3Na  OBr  =  N,  +  CO^  -f  2H2O  +  3NaBr. 

\NH, 

CO2  combines  with  the  NaOH  in  the  mixture. 
Each  cc.  of  N  ^  .00282  gr.  urea. 


^lifu 


to. 


i^^^J^  ^-^ 


CriOxxuS^.ttHxi*' 


/»■ 


C  =  e 


orvH-</ 


(J  IV  ^a 


hH 


/y 


/VH. 


98  PHYSIOLOGICAL   CHEMISTRY. 

What  is  uric  acid?     How  does  it  exist  in  the  urine? 

Uric  acid  is  tri-oxy  purin,  being  closely  related  to  the 
nuclein  base  compounds.  It  is  more  complex  than  urea 
and  is  capable,  upon  decomposition,  of  yielding  two 
molecules  of  urea.  It  occurs  not  as  free  acid  but  as  acid 
salts,  urates  (Na  and  K),  and  to  a  less  extent  with 
Ca  and  NH^. 

Give  the  properties  of  uric  acid. 

Uric  acid  is  a  di-basic  acid.  It  crystallizes  in  charac- 
teristic shapes,  the  pure  crystals  being  colorless,  those 
from  urine  a  very  reddish-brown,  due  to  the  pigment 
uroerythrin. 

Uric  acid  is  soluble  only  in  alkalies  as  NagCOg.  Its 
salts  are  soluble  in  alkalies  and  dilute  acids.  Other 
things  being  equal,  they  are  more  soluble  in  warm  than 
cold  solution.  Hence,  when  urine  cools,  there  is  fre- 
quently the  so-called  "  deposit  of  urates."  These  salts  are 
held  in  solution  in  the  warmer,  slightly  acid  urine. 

What  is  the  origin  of  uric  acid? 

Uric  acid  has  a  two-fold  origin : 

1.  Endogenous,  due  to  the  metabolism  of  the  nucleins 
of  tissue  cells. 

2.  Exogenous,  due  to  the  amount  of  free  or  combined 
purin  bases  in  food.  In  health,  the  factor  determining 
the  amount  of  uric  acid  is  the  quantity  of  purin  bases  in 
the  food ;  that  due  to  endogenous  origin  is  trifling. 

Although  uric  acid  upon  oxidation  yields  urea,  it  is 
not  a  product  due  to  lack  of  oxidation  but  to  a  different 
type  of  oxidation. 

How  may  uric  acid  be  prepared? 

To  a  large  beaker  of  urine,  add  lo  c.c.  dilute  HCl 
(or  H2SO4).  Stir  thoroughly  and  set  aside.  The  uric 
acid  crystallizes  out  in  characteristic  "  whetstone  "- 
shaped  crystals. 


lOO  PHYSIOLOGICAL    CHEMISTRY. 

What  is  the  origin  of  the  urinary  pigments?     Briefly 
describe  each. 

The  urinary  pigments  come  indirectly  from  the  hemo- 
globin of  the  blood,  and  directly  from  the  bile  pigments. 
The  most  important  pigments  are  urochrome,  uroery- 
thrin,  urobilin  and  hemataporphyrin. " 

Urochrome  predominates  and  the  color  of  normal 
urine  depends  chiefly  upon  it.  Uroerythrin  is  not  always 
present  and  when  present  is  held  in  the  uric  acid  crys- 
tals, giving  them  their  reddish  color.  Urobilin  is  con- 
spicuous in  fevril  urine.  Hemataporphyrin  is  a  normal 
constituent,  being  present  in  very  small  quantity. 

How  may  creatinin  be  separated  from  urine? 

To  urine  (750  c.c.)  add  150  c.c.  of  milk  of  lime  (Ca 
hydroxide  and  Ca  oxide).  Filter.  The  filtrate  contains 
all  the  creatinin  and  organic  substances.  Neutralize,  and 
set  aside  for  evaporation  in  the  hood.  Treat  the  evapo- 
rated residue  with  alcohol.  Filter.  The  filtrate  contains 
the  creatinin,  urea  and  pigments.  To  this  solution  add 
a  small  amount  of  alcoholic  ZnCU.  The  creatinin  forms 
a  molecular  combination  with  this  salt,  and  upon  stand- 
ing, crystallizes  out  as  creatinin  ZnCl,.  This  salt  is 
readily  soluble  in  water. 

How  would  you  test  for  indican  in  urine? 
What  is  the  significance  of  the  indican? 

Jaife's  test  is  employed  for  detecting  indican  in  urine. 
Add  an  equal  volume  of  concentrated  HCl  to  a  test-tube 
of  urine.  Add  10-15  drops  of  chloroform.  (A  few 
drops  of  an  oxidizing  agent,  as  potassium  permanganate 
is  often  added  to  favor  the  oxidation  of  indican  to  indigo.) 
Shake  thoroughly.  The  chloroform  sinks  to  the  bottom, 
carrying  with  it  the  blue  pigment,  indigo.  The  amount 
of  indican  in  the  urine  is  an  indication  of  the  amount  of 
putrefaction  occurring  in  the  intestines.  Indigo  never 
occurs  in  normal  urine,  and  only  rarely  in  abnormal 
conditions. 


I02  PHYSIOLOGICAL    CHEMISTRY. 

Write   the   reaction   showing   the   formation   of   blue 
indigo  from  indican. 

The  indican  is  first  changed  back  to  indoxyl.  Two 
indoxyl  molecules,  by  oxidation,  then  unite  to  form  one 
molecule  of  blue  indigo  and  two  of  water,  thus : 

COCSOgK)  C-OH 

I.     CgH,       CH  +  HCL  +  H2O  =r  CfiH,     CH  +  H^SO^  +  KCL 

NH  NH 

Indican.  Indoxyl. 


2.     C.H. 


COH      -f 

+  ' 

+       HiOC 

\    /  

NH 

CO 
/\ 

3.     c,u,     c 

NH 

Blue 

.    \       / 

NH 
CO 

/\ 
=  C        QH,     +2H,0 

\/ 
NH 

indigo. 

How  would  you  separate  oxalic  acid  from  urine? 

To  a  beaker  of  urine,  add  several  ex.  of  CaCls-  Make 
the  solution  slightly  alkaline  with  ammonia.  This  favors 
the  formation  of  Ca  oxalate  and  the  precipitation  of 
earthy  phosphates.  After  standing  for  15  minutes,  add 
acetic  acid  till  the  reaction  is  just  acid. 

The  phosphates  dissolve.  Set  aside  till  the  next  period 
when  crystals  of  Ca  oxalate  will  appear.  Under  the 
microscope  these  show  octahedral  shapes. 

What  are  the  leading  abnormal  constituents  of  urine? 

The  leading  abnormal  constituents  are  proteids,  sugars, 
constituents  of  blood,  and  constituents  of  bile. 

What  are  the  abnormal  proteids  found  in  urine? 

Albumins,  globulins,  alkali  albuminates,  proteoses  and 
peptones.  Mucous  and  epithelial  cells  are  normal  con- 
stituents. 


I04  PHYSIOLOGICAL    CHEMISTRY. 

What  sugars  are  present  in  urine  normally  and  ab- 
normally? 

Monosaccharides. 

Dextrose. 

Levulose. 

Pentose. 
Disaccharides. 

Lactose. 

Maltose. 
Polysaccharides. 

Dextrin. 

"  Animal  gum." 

Glycuronic  acid. 

Chondroitin  H2SO4. 

Describe  the  chemicarchanges  which  urine  undergoes 
during  alkaline  fermentation. 

Normal  urine  is  acid,  clear,  has  a  characteristic  odor 
and  there  is  no  precipitate.  In  24  to  48  hours  the 
acidity  is  reduced,  the  fluid  becomes  cloudy,  the  odor 
is  abnormal  and  a  slight  sediment  is  apparent.  Upon 
further  standing,  the  reaction  becomes  alkaline,  the  solu- 
tion becomes  very  turbid,  there  is  a  distinct  precipitate 
and  a  strong  abnormal  odor.  The  color  is  unchanged. 
Crystals  of  magnesium  ammonium  phosphate  appear 
on  the  side  of  the  flask  and  there  is  a  strong  odor  of  NH3. 
This  fermentation  is  due  to  the  action  of  organized 
ferments. 


COMMON    TESTS    EMPLOYED    IN     PHYSIO- 
LOGICAL   CHEMISTRY. 

Acrolein  Test  (for  glycerin  radicals  in  fats). — Add  a 
few  crystals  of  K  bisulphate  to  the  suspected  substance. 
Heat.  The  odor  of  burning  tallow  indicates  the  presence 
of  glycerin. 

Biuret  Test  (for  proteids). — To  a  proteid  solution 
made  distinctly  alkaline  with  KOH,  add  a  very  dilute 
CUSO4  solution.    A  reddish-violet  color  results. 

Calcium  Test. — Add  ammonium  oxalate.  There  will 
be  a  white  precipitate. 

Chloride  Test. — Acidify  with  nitric  acid  and  add  silver 
nitrate.     White  precipitate  falls. 

Cholesterin  Iodine  Test. — To  cholesterin  crystals  on 
a  microscope  slide,  add  a  drop  of  dilute  iodine  solution. 
Put  on  cover  slide  and  allow  a  drop  of  concentrated  sul- 
phuric acid  to  ooze  under.  A  series  of  colors,  from 
brown  through  green  to  blue,  will  follow  the  line  of  ad- 
vance of  the  acid. 

CO  2  Test. — Add  dilute  acid,  as  acetic.  Effervescence 
indicates  a  carbonate. 

Fehling's  Test  (for  sugar). — Warm  some  Fehling's 
solution  and  add  the  suspected  carbohydrate  solution  (pre- 
viously made  alkaline  with  KOH)  and  warm  again. 
Yellow-red  reduction  indicates  presence  of  sugar  (glu- 
cose). 

Gmelin's  Test. — To  some  bile,  in  an  evaporating  dish 
add  a  few  drops  of  nitric  acid  containing  nitrous  acid. 
There  will  be  a  series  of  colors  from  green  to  a  reddish- 
yellow. 

Guaiacufrt  Test  (for  hemoglobin). — To  a  dilute  solu- 
tion of  suspected  blood  add  a  few  drops  of  guaiacum 
tincture  and  a  few  drops  of  turpentine.  A  bluish  zone 
results  if  hemoglobin  is  present. 

Gilnzherg's  Test  (for  free  HCl). — Warm  a  small 
amount  of  the  indicator  in  an  evaporating  dish  until  all 
traces  of  alcohol  have  left.  Then  add  a  drop  of  sus- 
pected solution.  If  free  acid  is  present  an  intense  red 
color  results. 


I08  PHYSIOLOGICAL    CHEMISTRY. 

Hemin  Test  (absolute  test  for  hemoglobin). — To  a 
drop  of  suspected  solution  on  a  cover  glass,  add  a  minute 
grain  NaCl.  Dry  carefully  over  flame  and  add  a  drop  of 
glacial  acetic  acid.  Cover  with  cover  glass  and  gently 
warm.  When  cool,  and  examined  under  the  microscope, 
crystals  of  hemin  will  be  seen  if  hemoglobin  is  present. 

Hofmann's  Test. — This  is  a  test  for  tyrosin  with 
Millon's  reagent.     Red  color  results. 

Iodine  Test. — This  is  a  test  for  polysaccharides.'  The 
iodine  solution  is  turned  blue. 

Iron  Test. — Add  HCl  and  K  ferrocyanide.  A  blue 
coloration  is  produced. 

laife's  Test  (for  indican). — To  some  urine,  add  an 
equal  volume  of  concentrated  HCl  (a  drop  of  K  per- 
manganate may  be  added  to  favor  oxidation).  Then 
put  in  a  little  chloroform.  Shake.  When  the  chloroform 
sinks  to  the  bottom,  it  will  carry  down  the  blue  indigo 
color  if  indican  was  present. 

Millon's  Test  (for  proteids). — Treat  the  proteid  with 
Millon's  reagent.  A  white  precipitate  is  formed  which 
turns  red  upon  warming. 

Molisch's  Test  (for  sugar). — To  the  sugar  solution 
add  a  few  drops  of  alpha-naphthol,  then  concentrated 
H2SO4  in  excess.    A  reddish  purple  zone  results. 

Moore's  Test  (for  sugar). — Add  KOH  to  the  sugar 
solution  and  heat.  Yellow  color  results  with  a  faint  odor 
of  caramel. 

Murexid  Test  (for  uric  acid). — Place  a  uric  acid 
crystal  in  a  porcelain  dish  with  a  drop  of  nitric  acid. 
Warm.  A  red  stain  results.  Cool  and  add  a  drop  of 
ammonia.    The  purple  color  of  murexid  results. 

Ny lander's  Test  (for  sugar). — Test  is  the  same  as 
Fehling's,  except  that  the  solution  is  an  alkaline  bismuth 
solution  instead  of  copper.  Heat  the  solution  with  the 
suspected  solution,  to  boiling.  A  black  deposit  results  if 
sugar  is  present. 

Pettenkofer's  Test  (for  bile  salts). — To  some  bile  in 
a  porcelain  dish,  add  a  grain  of  sugar.  Then  drop  in 
from  a  pipette,  concentrated  H0SO4.  A  brilliant  cherry- 
red  color  results. 

Phenyl  hydrazine    Test    (for    sugar). — To    the    sugar 


i/^. 


no  PHYSIOLOGICAL    CHEMISTRY. 

solution  add  a  spoonful  of  sodium  acetate  with  phenyl- 
hydrazine  hydrochloride.  Boil  and  allow  to  stand  24 
hours.     Characteristic  crystals  will  form. 

Phosphoric  Acid  Test. — Acidify  with  nitric  acid  and 
add  molybdic  solution.  Warm.  A  yellow  color  (fine 
precipitate)  will  result. 

Potassium-  Siilfo-cyanide  Test. — Acidify  with  HCl  and 
add  a  drop  of  ferric  chloride.     A  reddish  color  results. 

Purin  Base  Test. — Make  the  solution  alkaline  with 
ammonia  and  then  add  an  ammoniacal  solution  of  silver 
nitrate.     A  brown  precipitate  results. 

Salkowski's  Test  (for  cholesterin). — Dissolve  the 
solid  cholesterin  in  chloroform.  Add  an  equal  volume 
concentrated  H^SO^.  Shake  thoroughly.  The  solution 
becomes  a  cherry-red  which  gradually  deepens  in  color. 

Schiif's  Test  (for  uric  acid). — Dissolve  a  few  crystals 
of  uric  acid  in  sodium  carbonate  and  put  a  drop  of  silver 
nitrate  on  a  filter  paper.  Add  a  drop  of  uric  acid  to  the 
filter  paper.  A  brownish  coloration  results  due  to  re- 
duction of  the  silver  salt. 

Sulphate  Test. — Acidify  solution  with  HCl  and  add 
barium  chloride.    There  will  be  a  white  precipitate. 

Tropaeolin  00  Test  (for  free  HCl). — Warm  a  small 
amount  of  the  indicator  in  an  evaporating  dish  till  all 
traces  of  alcohol  are  gone.  Upon  adding  the  suspected 
substance  and  warming,  a  purple  color  results  if  free 
acid  is  present. 

Uffelmann's  Test  (for  lactic  acid). — The  suspected 
solution  is  added  to  Uffelmann's  reagent,  carbolo-ferric 
chloride.  If  lactic  acid  is  present,  the  purple  color 
changes  to  yellow. 

WeyVs  Test  (for  creatinin). — Make  the  creatinin  solu- 
tion alkaline  with  KOH.  Add  a  drop  of  Na  nitro-prussid. 
A  red  color  results  which  is  destroyed  by  acidification. 
Acetone  responds  to  the  test  but  the  color  does  not  disap- 
pear upon  acidification  (Legal's  test). 

Xanthoproteic  Test  (for  proteid). — Add  concentrated 
nitric  acid  in  excess  to  the  proteid  solution.  Heat  until 
a  distinct  canary-yellow  color  appears.  Cool.  Then  add 
ammonium  hydroxide  in  excess.  An  orange  color 
results. 


PAST    EXAMINATION    PAPERS. 

I.  (a)  In  what  forms  does  uric  acid  exist  in  the 
urine?  (b)  Explain  the  spontaneous  sep- 
aration of  uric  acid  from  urine  and  write 
reaction  to  illustrate  the  same. 

11.  (a)  Name  the  chief  substances  present  in  normal 
faeces,  (b)  Explain  the  occurrence  in  the 
faeces  of  five  of  these. 

III.  What  substances  appear  to  be  the  immediate  pre- 

cursors in  the  body  of  (i)  melanin,  (2) 
hippuric  acid,  (3)  dyslysin,  (4)  hydro- 
chloric acid,  (5)  urea,  (6)  creatinin,  (7) 
indican,  (8)  pepsin,  (9)  bilirubin,  (10) 
arabinose  ? 

IV.  (a)   State  the  essential  characters  of  the  following 

kinds  of  phosphates :  (i)  alkali,  (2)  earthy, 
(3)  alkaline,  (4)  acid,  (5)  acid  alkali,  (6) 
"  stellar,"  (7)  "  triple,"  (8)  tri-basic.  (b) 
Illustrate  with  formulae. 

V.  (a)  What  substances  are  particularly  prominent 
in  the  cell?  (b)  Distinguish  between  pri- 
mary and  secondary  constituents,  (c)  Give 
three  typical  examples  of  each  group. 

VI.  How  would  you  separate : 

(i)   Proteose   from   a   solution   containing  also 
peptone  and  mucoid? 

(2)  Dextrin   from  the   products   of   a   salivary 

digestion  of  starch? 

(3)  Lecithin   from  an  alcoholic  brain   extract? 

(4)  Purin  bases  from  meat  extract? 

(5)  Caseinogen  from  milk? 

VII.  Describe  in  some  detail  the  chemical  changes  oc- 
curring in  respiration. 

VIII.  What  functions  are  performed  in  the  body  by  (i) 
oxygen,  (2)  water,  (3)  glycogen,  (4)  fat, 
(5)  intestinal  juice? 


114  PHYSIOLOGICAL    CHEMISTRY. 

IX.  Write  reactions  to  show : 

(i)   Formation  of  lactose  from  dextrose. 

(2)  Precipitation  of  tri-basic  calcium  phosphate 

from  a  solution  of  soluble  calcium  phos- 
phates on  heating. 

(3)  Production  of  nitrogen   from  urea  in  the 

''  hypobromite  process." 

(4)  Synthesis  of  carbohydrate  from  inorganic 

radicles. 

(5)  Derivation  of  aceton  from  fatty  acid. 

X.  Indicate  the  (a)  physical,  (b)  chemical  and  (c) 
functional  qualities  of  bile  and  state  the  (d) 
fate  of  its  constituents. 

I.  (a)  What  are  some  of  the  metabolic  products  of 
hemoglobin?  (b)  Where  are  they  con- 
spicuous? (c)  In  what  forms  do  they  leave 
the  body? 

II.  Name  the  substances  upon  which  the  more  con- 
spicuous functions  of  the  following  depend : 

(i)  epidermis,  (2)  bone,  (3)  tendon,  (4) 
bile,  (5)  gastric  juice,  (6)  succus  entericus, 

(7)  muscle,  (8)  suprarenal  gland,  (9) 
mixed  diet,  (10)  lymph. 

III.  (a)   Describe   the   chemical   changes   which   urine 

undergoes  during  alkaline  fermentation. 
(b)  How  would  you  recognize  such  a  con- 
dition of  the  urine? 

IV.  (a)   Indicate  the  varieties  of  chemical  and  physico- 

chemical  processes  occurring  in  the  body. 
(b)  Give  illustrations  of  some  of  the  more 
important  of  these. 

V.  Describe  two  of  the  best  methods  for  proving  the 
presence  or  absence  of  bile  in  the  urine. 

VI.  (a)  Name  substances  which  are  present  in  all  the 
tissues,  (b)  What  substances  are  found 
only  in  the  connective  tissues? 

VII.  Write  reactions  typifying  the  changes  which  car- 
bohydrates undergo  in  organisms,  showing 


Il6  PHYSIOLOGICAL    CHEMISTRY. 

(i)   Production    of   polysaccharide    from    inor- 
ganic radicles. 

(2)  Hydrolysis  of  polysaccharide  to  monosac- 

charide. 

(3)  Inversion  of  disaccharide. 

(4)  Regeneration  of  polysaccharide  from  mono- 

saccharide. 

(5)  Oxidation  of  any  form  to  inorganic  radicles. 

VIII.  Indicate  the  nature  and  extent  of  the  chemical 
changes  which  proteids,  fats  and  carbohy- 
drates undergo  in  the  gastro-intestinal  canal 
before  they  or  their  products  are  absorbed. 

IX.  Given  a  sample  of  dry,  powdered,  secondary  pro- 
teose, (a)  To  what  characteristic  tests 
would  the  material  respond?  (b)  How 
would  you  proceed  to  determine  whether 
gelatin  was  or  was  not  admixed  with  it? 

X.  Where  in  the  body,  and  in  what  combinations,  do 
or  may  the  following  acids  occur :  ( i )  ben- 
zoic, (2)  glycuronic,  (3)  oxalic,  (4)  car- 
bonic, (5)  propionic,  (6)  phosphoric,  (7) 
lactic,  (8)  butyric,  (9)  sulphuric,  (10) 
palmitic  ? 

I.  Describe   the   physico-chemical   conditions   of   the 
contents  of  the  cell. 

II.  What  are  the  chemical  and  metabolic  properties 
of  (a)  iodothyrin  and  (b)  thyreoglobulin? 

III.  Indicate  the   (a)  composition  of  the  liver,  its   (b) 

functions    and    the    various    (c)    reactions 
taking  place  in  it. 

IV.  (a)   Name  the  leading  constituents  of   (a)   wheat 

flour,  (b)  potato  and  (c)  bread. 

(b)   How  may  the  most  conspicuous  in  each  be 
identified  ? 

V.  What  are  the  functions  of  (a)  erepsin,  (b)  secretin 
and  (c)  enterokinase  ? 


Il8  PHYSIOLOGICAL    CHEMISTRY. 

VI.  Name  the  varieties  of  fermentation  in  the  gastro- 
enteric tract  and  state  the  conditions  there 
influencing  the  process. 

VII.  Write  reactions  to  show : 

(a)  Formation    of    carbon    dioxide    from    gly- 
cogen. 

(b)  Transformation  of  creatin  into  creatinin. 

(c)  Derivation  of   urea   from   ammonium   car- 

bamate. 

(d)  Synthesis  of  carbohydrate  from  inorganic 

radicals. 

(e)  Production  of  glycuronic   acid   from   dex- 

trose. 

VIII.  What  are  some  of  the  chemical  defences  of  the 
organism  against  disease? 

IX.  Give  the  name  of,  and  describe,  at  least  one  fa- 
miliar test  for  each  of  the  following  sub- 
stances:  (a)  sodium  glycocholate,  (b) 
maltose,  (c)  indican,  (d)  creatinin,  (e) 
cholesterin,  (/)  uric  acid,  (g)  tyrosin,  (h) 
aceton,  (/)  diacetic  acid,  (/)  tryptophan. 

X.  Show,  with  the  aid  of  formulae,  the  resemblances 
and  differences  among  the  following  prod- 
ucts:  (a)  tyrosin,  (b)  tryptophan,  (c)  in- 
dol,  (d)  indoxyl,  (e)  indican,  (/)  blue 
indigo. 

I.  What  are  the  general  characters  of  chemical 
change  (a)  in  the  living  body,  (b)  in  the 
dead  organism,  (c)  in  plants  as  contrasted 
with  animals? 

II.  (a)  Describe  the  acrolein  test.  (b)  Write  the 
reaction  involved.  (c)  Name  the  sub- 
stances that  will  respond  to  the  test. 

III.  What  is  the  relation  of  nerve  and  muscle  to  the 

transformation  of  energy  in  the  body? 

IV.  Describe  the  chemical  changes  involved  in  the  ab- 

sorption  of   three   typical   classes   of   food- 
stuffs. 


120  PHYSIOLOGICAL    CHEMISTRY. 

V.  (a)  How  may  urea  be  separated  from  liver  and 
identified?  (b)  Show,  with  formulas,  the 
relation  between  ammonium  carbonate  and 
urea. 

VI .  Describe  methods  for  the  separation  from,  and 
identification  in  egg  yolk,  of  lecithin,  choles- 
terin  and  fat. 

VII.  (a)  Name  the  leading  constituents  of  (a)  tendon, 
(b)  suprarenal  gland,  (c)  epidermis,  (d) 
bile,  (e)  bone,  (/)  milk,  (b)  State  the 
chief  functions  of  each  constituent  named. 

VIII.  (a)  Write  reactions  showing  the  relations  of  B- 
oxybutyric  acid  and  diacetic  acid  to  acetone. 
(b)  What  are  the  biological  sources  of  these 
substances?  (c)  What  is  their  significance 
in  the  urine  ? 

IX.  (a)  What  are  the  leading  constituents  of  proto- 
plasm? (b)  State  the  physico-chemical 
condition,  in  the  cell,  of  these  constituents? 

X.  Where  in  the  body,  and  in  what  combinations,  may 
the  following  occur:  (a)  glycuronic  acid, 
(b)  iron,  (c)  acetic  acid,  (d)  cholin,  (e} 
indol,  (/)  chondroitin  sulphuric  acid,  (g) 
glycerin,  (h)  ammonia,  (i)  propionic  acid, 
(/)  purin  bases? 

I.  Name  the  principal  organic  constituents  of  urine. 
What  is  the  metabolic  significance  of  each? 

II.  Explain  the  need  of  the  organism  for  proteid  food. 

III.  Trace,  step  by  step,  the  changes  that  food  albumin 

undergoes  in  its  conversion  into  serum  al- 
bumin. 

IV.  Where  in  the  body,  and  under  what  conditions, 

may  the  following  substances  be  formed: 
creatin,  dyslysin,  triple  phosphate,  sodium 
palmitate,  dextrose,  cholesterin,  glycogen, 
tyrosin,  ammonia,  hematin? 


122  PHYSIOLOGICAL    CHEMISTRY. 

V.  How  may  glycerin  be  prepared  ?  Mention  its  lead- 
ing properties. 

VI.  State  the  chemical  nature  and  relationships  of 
tryptophan. 

VII.  How  does  muscular  contraction  affect  excretion? 

VIII.  What  are  enzymes,  zymogens,  anti-enzymes,  anti- 
toxins ?    What  are  their  chemical  functions  ? 

IX.  How  may  iron  albuminate  be  prepared  from 
liver?  What  is  peculiar  about  the  iron  in 
that  substance? 

X.  Write  the  constitutional  formulas  of  the  following 
substances  :  glycocoll,  leucin,  tristearin,  am- 
monium carbamate,  glycuronic  acid,  uric 
acid,  lactic  acid,  skatol. 


2 


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